I think the best one I have seen is the GoCycle G3.... in terms of weight, space when folded, range... etc.... but it costs more than I would spend on a motorcycle!! Brompton bicycles are pretty good space & weight wise, but again quite expensive too.
This is the hardest bit of flying, how do you get from the airfield to other places. Taxi is often be the best method, but can be quite expensive.
In the US, I have seen airports offer courtesy cars, that pilots coming in can just borrow, keys on the wall type deal with a "please bring back with full tank" note. It's a shame that this isn't customary in the U.K. But then again who would foot the bill for the MOT, insurance... etc....?