If i was to build an electric car what sort of DC motor would i need and where might i find one?? What sort of cost is it likely to be??

Old milk float?

Forklifts would be the other obvious source for traction motors. Older forklifts were all DC but most newer have switched to AC as the motors are quieter.

Lynch make suitable motors. You'll need a healthy bank balance though.

Lots of links to EV parts suppliers here

Don't they like noisy cars in Chelmondiston then Doug?

I'm already in trouble if they do...

you could check the breaker yards for a toyota hybrid ! it also has the worlds best lithium ion batterys!!