The idea of flying Harvards was partly to do with getting time on fairly powerful vintage machines which might take part at air shows so that I might be able to fly it in one after a while and eventually move onto other vintage planes because unless you;ve got time on machines like harvards no one would ever think of allowing you to display their aircraft. People who fly spitfires have to learn on other machines like harvards which is what they used in the war before they converted onto type. For example if your company had a share in a spitfire then who would you be looking for as potential pilots for it: someone with 500 hrs on a cessnas or someone with time on Tiger Moths and Harvards?
Its very unlikely that I'd ever get to fly a spitfire but harvards are a good plane to fly to make it more likely and chipmunks and yaks would not benefit you in the same way.
However chipmunks and yaks are very good suggestions. I know chipmunks could be around £130 an hour, I think there's one at Liverpool and another at Booker for about that, but how much is a Yak 52?