Yorks.ppl
As far as I'm aware there is no legal requirement for any of your hours to be cross crountry when revalidating/renewing your PPL. You just have to have the requisite number of hours and take off's and landings.
The only thing that I can think of were there is a requirement for a minimum number of hours of cross country is for starting an IMC rating. However its a long time since I did my initial IMC training, so things may have changed since then.
Brooklands