In reply to tim_broadhurst:
Well overall volume will help - I would keep the cycling low effort though - I don't know what sort of approach you naturally take but from your post I think you should regard it as 'active recovery' effort and not much more.
If you have the time then some sessions of these will help. (anything up to an hour a day - if it is easy it can go on top of running efforts)
You could also put a long ride (3hours plus) at easy (easy!!!) effort in weekly with little extra training load but the benefit of getting used to moving for longer periods of time. Harder to do running.
Finally, if your run style is good (higher cadence) then you could keep your cycling at lower cadence (sub 80, aim for 70) , this will build leg strength for the hills and reduce overall aerobic load.
Just some ideas