There's is no way that anyone can run an RG shop and have a cafe such as you suggest in the UK without finding they run the risk of finacial collapse in half the time of any normal store.
Honestly, half the shops without food suffer financial collapse just the same - I don't think there's a difference in the risk, with or without food sales, RPG shops are risky operations, no matter what other conditions are met.
There's the health and safety rules covering food prep that require the preparer to have appropriate certification (to avoid poisoning the customers) that's a considerable cost and makes the shop subject to periodic inspections. Next assuming you find someone cheap enough then the matter of zoning rear's it's ugly head. It may not be possible to change the zoning for the shop to accommodate a cafe.
In the US, a food health certification is like $50 and a 90 day class at the local community college (its no big deal), and most health inspections happen once at the start of operations and periodically, often several years apart. Again, you keep a clean kitchen and follow the health rules - its no big deal.
The OP has no experience in running any sort of retail operation and adding in the food idea is just extra madness. Assuming he get's all his ducks correctly lined up and opens evenings only to start that is more likely to slow down the inevitable collapse. His best chance is to take professional advice from appropriate people and not rely on the random strangers inhabiting a board on a site not related to the business at all.
I don't know what the OP has experience with, but most people I know in both game shops and small restaurants have zero experience in retail and food service, but doesn't seem to stop the inexperienced from opening such businesses. And of course, it would be silly not to rent/lease/buy a building that doesn't already have an existing commercial kitchen, if you intended to open a game shop cafe. The cost of equipment, not to mention the grease ventilation and fire-suppression system would be too costly to install brand new for such an intended cafe. Of course there ought to be plenty of available properties that have an existing kitchen. The kitchen area needs only be a prep area, flat grill, a deep fryer, a freezer and refrigeration - it doesn't even have to be a separate room (though would be better if it were).
And perhaps, I am a "random stranger inhabiting a board", but I am also an experienced restaurant owner/operator, have run a graphic design studio and digital print shop for 20 years with some level of retail in my shop. Aside from the graphics schooling, I had no official training in food service nor retail, yet ran successful businesses for over 25 years. Maybe such options are too difficult for you, but IME, its no more challenging than anything else in life. In my case aside from some jobs held during and shortly after college, my entire life experience has been in self employment by running businesses, and I've never found that life over-challenging (I'd go as far as calling it work, but relatively easy work).
But don't let facts spoil anyone's chances of throwing a useless comment into the thread.
I'd consider anyone opening an RPG game shop alone to be the most risky proposition, doing so as a cafe, I'd consider much smarter and better investment than the former. Perhaps my comment is useless to you, but if you have half-a-brain, I'd think the value in my comment would be most welcome. Running retail and food service both involve work, keeping operations clean and efficient, but that's true with most things - it's not rocket science, though.
