Originally Posted by Gonzo Bob

Maybe. A 700C wheel will certainly fit in a frame designed for 27" wheels since it is a little smaller (4mm smaller radius). But there could be an issue getting to brakes work as it might not be possible to lower the brake pads enough to contact the rim. For caliper brakes, a solution to this would be drop bolts. For cantilever or v-brake, the solution would be to have a frame builder lower the posts.