A coffee shop in the UK is going to get shut down as cannabis is still illegal.
I owned a coffee shop in Holland and it was no easy task getting all the right paperwork and licences but other than that it is no different to having any other kind of business serving the public.

Number of coffee shops dropped - Government.nl

As a coffeeshop you can sell up to 5 grams of cannabis per transaction as long as it follows five rules: no minors, no alcohol sales, no hard drug sales, no advertising and no "public nuisance."