Opening a new shop.

however my pal does want to make some money out of this......

Gotta spend to make money, like actually need to take out a loan.

He need to get brand everyone know and easy to sell, and jump on the ebikes wagon as well as making sure the mechanics are trained and up to date.

He gonna have to deal with a LOTS of warranties compare to just running a workshop.

Loads of different ideas and perspectives are good just incase someone touches on something that you'd wished you'd thought of but hadn't but don't let yourself get swayed too much by others. Once you have a clear idea of which direction you want to go in if that vision is welcomed and reinforced by others that probably makes for a more solid plan.

To all that have mentioned coffee, there is a bakery chain next door but one who do fine coffee

Maybe work out some deal with them where people get a free coffee with every service (purchase over £xxx, etc.)? Your mate pays for the coffee at cost, free coffee people also buy a cake, they enjoy their coffee and cake and the experience stays with them, they tell their friends, everyone wins.

however my pal does want to make some money out of this......

Boring, but the key advice i've been given consistently when going down this road is to understand the numbers. Getting a grip on the business aspects may help your friend determine what is actually feasible/realistic. Maybe worth looking into a business course or as someone mentioned speaking to a business consultant. Something that's always stuck with me is that good business people generally love business, not the business.

In terms of daily revenue/passing trade another tip i've been given is that especially in hard times people love cheap sub £5 rewards to themselves. By my understanding this is part of the reason coffee has done so well. I'm sure there's other options but you shouldn't ignore the environmental impact of such stuff.

Regarding boutiquey places, the ones i know here (lifestyle, not bike) are started by people with major capital (ex bankers etc) and essentially exist on selling back to there network of rich contacts. Blue Lug have mega outreach and AFAIK do well but there's plenty of boutique bike shops in Tokyo that could only exist with financial support.