D Ward
In answer to your question on size required, around 1200sqft which should include at least one office, toilet &kitchen area. A round here prices are £4.5k to £5.5 for that sort, but, you need to allow for rates which is approx 50% o annual fee (This can be halved with local council small business reduction if it applies)
I have 750sqft, in mine i have locker area, storage area, various equipment, sink with coing & tea making facilites, washer & tumble dryer. A 3500 static tank &ro. Pressure washers, storage cupboard & portable system. Work bench, tools & spares, these are all on outside wall & finally we can fit 2 vans in.
So as you can see you can fit a lot in a small unit, mine is£300 per month & all bills. But its a faily new modern pupose built one on an estate.
I have also seen Robs unit & that is more than twice the size of mine, & exceptional good value & is very good unit. Take Robs advice & approach farmers etc as you do get a very ood deal
Gary