Martin Lewis is about to become a grandfather. Or an uncle. He can't be sure which. But that's families for you. Virtual ones anyway.

What he does know for sure is his relationship with the financial powerhouse he gave life to in 2003 is about to change - again.

Three years after he sold his online MoneySavingExpert business for more millions than he'd ever dream of spending on himself, he is leaving the editor's chair he retained as part of the deal and taking yet another role.

This time it's as the rather grander sounding executive chairman, a job he hopes will occupy him around eight days a month and allow him to play a wee bit more golf and oversee everything from a distance. But there's a long way to go before that happens.

We're sitting in a glass box in the West End office block he shares with his new owners, the moneysupermarket.com group. Outside, a staff of almost 100 are busy updating what has become possibly the most dependable resource anywhere for anyone interested in spending sensibly.

I still don’t like to spend a penny more on things than they should cost

He's smartly dressed in Massimo Dutti jacket and blue slacks. And he's sitting across two seats, feet up on one of them. I see he's wearing trainers (problems with his arches - these are more comfy) and not the designer kind. It's trite to ask but I can't resist it.

So, how much did that jacket cost?

"Ninety pounds. Half price in a sale," he says. And that's fine for Lewis. If you know what he's about, you'll know it's not scrimping, it's about value. Spend, but spend well. And sensibly.

"I don't have designer clothes. I buy off-the-peg and I generally buy in the sales. I just don't get the label thing. I can't see the point of a £1,000 suit. And I hate paying more than £50 for shoes. My wife generally feels the same but shoes are the one thing we disagree on.

"In fact, we would go somewhere where there were paps and the the papers would say this one was wearing Gucci, this one Armani and Lara [Lewington, his TV presenter wife of seven years] was wearing Primark. But we don't mind. Neither of us has expensive tastes.

"It's different with technology. I'd buy an expensive TV, something that was worth it. But I'd spend because something was good, not because something says it's good.

"The Telegraph said I still shop in Poundland but why wouldn't I? And then the Mail reported that I was seen in a queue for easyJet - and asked why wasn't I on a private jet? You can't win."

To be fair, he's used to it. Everyone he meets wants a tip. Casual acquaintances, people in the street, the film crews he works with.

"Everyone tells me I'm doing something wrong. They say, if it was me, I'd be doing it like this or that. But I don't mind, I do tend to give everyone time and, listen, I even get some great tips sometimes. Generally, it's a joy. But I tend not to answer business questions. People do tend to pitch them to me at Jewish events but I'm not an entrepreneur, I'm a money-saving expert.''

And at shul? He goes to the Saatchi Synagogue in St John's Wood.

"It's quite small, growing I have to say, but small and has a great rabbi in Rabbi Mendel [Cohen]. To be honest, I tend not to get bothered there. People do talk to me but if I am in shul I am there on Shabbat and I prefer not to talk about work."

So, let's talk about it now. Martin Lewis OBE, a Mancunian headmaster's son who grew via a career writing and broadcasting to become the biggest name in personal finance after launching MoneySavingExpert.com for, give or take a few bob, £80 in February 2003.

In September 2012 he sold it to the Moneysupermarket group in a deal reportedly worth more than £80 million, split between cash, shares and future payments. He then promptly announced his intention to give £10 million away to charity.

While the deal meant he never had to work again, one gets the impression that was - and probably is - never going to happen. A bonus was the agreement that he should remain as editor-in-chief, which meant he could be sure it retained the values he had imposed from the start.

To police that, he had a legally-binding code of conduct drawn up to make sure. All new staff have to read it and agree to be bound by it.

"Any breach of that would have substantial penalties," he says. "It ensures what we write is in the public interest and not the interests of profit. You won't find anyone pressuring us to, for example, link to this product over that. We are entirely independent."

Until now, his role has been more akin to that of a CEO. Sure, he's been immersed in the content but he's otherwise been running the show: overlooking the technical stuff, making sure bills get paid.

The new structure will see his head of operations become MD, a new editor-in-chief will be appointed in time - he knows it's a tough role to fill and anyone decent will have a long notice period - and he will sit on high, pulling strings as and when necessary, which effectively means he'll line manage his replacement while concentrating on strategy and those all-important ethics.

I suggest he's stepping aside and he cuts in. "More a case of stepping back. I see this more as a promotion. I'm not letting go. It's still my passion, still my baby. I'm just moving from parent to grandparent."

Grandparent? He told his last interviewer he was going from father to uncle. "Did I? " he asks with a smile. "OK. Ask me in a year's time which analogy works best."

Cynics have already been quick to question how the brand can continue to thrive without his name behind it. He doesn't see that as a problem. For one thing this will be a gradual process. For another he's already begun distancing himself. Have a read. Opinion is more and more being expressed as "we" rather than "I". His picture will start to become less evident throughout the site.

"It has to stand alone at some stage and be able to deliver in its own right," he says. Will readers disappear? "My job as executive chairman will be to ensure they don't. But eventually, if it was a case of me leaving in a good way, that would be fine. If it was because I didn't believe in what it was doing any more, I would be very hard on it."

There would be nothing, if ever he needed to assert his site's independence, to stop them "slagging off Monseysupermarket" if was in the consumer's interest.

"So far, it has been a good marriage and I've been happy to stay in it. Moneysupermarket is a comparison site and we are an editorial one. My MD is a brilliant man and we share the same instincts. Spot-on, in fact."

And while we're on those relationship analogies again, did they have to work at that marriage or was it love at first sight?

"Like any form of courtship, it involved a bit of dancing before we sealed the deal."

He eventually sees himself adopting a more "portfolio" lifestyle, combining perhaps a little more leisure with spreading himself to projects where he can add value.

"For years, my entire life has been focused on Tuesdays , the day the weekly email is prepared to be sent to almost 11 million people. They were days that began at 8.30 and went on until midnight. Someone else can do that in future."

Series Five of the Martin Lewis Money Show begins shortly and he tells me with delight it will be scheduled on Mondays over the four weeks running up to Christmas before returning to Fridays afterwards - "which means those who observe Shabbat can watch it".

So, back to saving money. To be clear, what sort of example is he setting?

"I enjoy five-star holidays but don't like to spend a penny more than it should cost. Don't confuse what I do with penny-pinching. I've had people tell me 'I went on honeymoon and stayed in a first-class hotel, you will probably hate me for it'. I say, if you're not in debt and didn't overpay for what you had, I wish you much mazel."

Are there exceptions?

He thinks for the briefest of moments.

"When I go to Kosher Kingdom before Pesach and someone asks, 'Can you save some money here?' I just say, 'No you can't - it is what it is.'"