My mrs is in the process of waiting for planning permission to open up a beauty salon, as the shop use is currently A1 and needs planning permission for change of use. This process can take up to 8 weeks apparently. Also our council charged us about £300 fee, whether or not it gets approved before our application can be processed. But as long as the previous use of shop you are renting is not going to affect the community, then you should be ok. This means say if the shop used to be a chemist and there isn't a chemist on that street, then you need to to argue why the change of use will not affect the locals in the area. So Basically as long as there are enough A1's and A2's ect, and not loads of sui generis's, then all should be ok.
Sui Generis - Theatres, houses in multiple paying occupation, hostels providing no significant element of care, scrap yards. Petrol filling stations and shops selling and/or displaying motor vehicles. Retail warehouse clubs, nightclubs, launderettes, dry cleaners, taxi businesses, amusement centres and casino's.
Basically from my understanding, it is buildings that need to operate large machinery and are need special attention with health and safety.
Hope this helps.
Thanks,
Matt