Sounds like a great idea mate, I hope you manage to get it working to great effect.
I found an ebay seller a while ago who has decent sized motors, though unfortunately he/she doesnt say the voltage or whether they are AC/DC. Might be worth a look, but not cheap, I think the prices have gone up recently.
eBay UK Shop - electric-motor-man: electric motor, single phase electric motor, three phase electric motor