Try Huws Gray (Warrington branch the best) not in your area but they should be able to advise you were to get a match. Call in to a local builders merchants they should also be able to tell you a local place.
You will need to dig out vegetation soil approx 500mm and place a minumin of 200mm cocrete. If you can get a 3 nuton block which are light it will give good strength and dont forget to build in piers approx every 5m in length, also by door openings.
