Sturmvogel it was the hangar at Rush Green I was thinking of. At the back there is an elevated section above the offices and stores which is big enough to rebuild a fuselage and wings. There is a chain hoist to lift things up and down. A Miles messenger wing (one piece 35' span was built up there a while ago. It is usually possible to create enough space to assemble an aircraft the size of a C150 at the back of the hangar with a bit of jiggery pockery with the resident aircraft.
Regarding the engine you might be better off buying a part lifed engine from the classified in the PFA magazine, Pilot. Alternatively check the aircraft breakers who specialise in buying aircraft wrecks / corroded hulks and breaking them for spares. You could probably get a 1,200 - 1,500 hour engine for around £4,000.