I also did an hour with an instructor earlier this year, as I didn't realise (owing to the fact the CAA told me otherwise) that an OPC can count. I don't know why the CAA didn't go fully with the FAA system like they did with the rest of the new JAA PPL details. Under FAA rules you need a check flight with an instructor every 2 years. Its a "flight review" which means just that. There is no set time. A good instructor will look at what you have done in the past 2 years and see what you need to brush up on. Perhaps you've only been doing long cross countries so need circuit practice and stalling, unusual attitudes, etc. Or perhaps you've just done a few circuits and not much cross country in which case he/she'll concentrate on that.
You don't get signed off until the instructor is happy that you are current once again on all procedures.
Sounds sensible to me.