When Roadford was built in the heart of Devon, SWWA said that Devon & Cornwall would never have to have standpipes again. Quite a few reservoirs both in Devon and Cornwall can be fed from Roadford via underground piping, so at least we will not go the same way as we did in 1976 if this weather continues.
I believe that any hosepipe ban only refers to domestic situations, although I do remember that commercial car washes had to close as the government banned the washing of vehicles except for number plates, windscreens, wing mirrors etc for safety reasons.
I expect that any hosepipe ban would start with a ban on domestic use and then ramp up to certain commercial enterprises if the weather continued to deplete the reservoir levels.