Don't know anything about the Canadian PPL really.
However, here is the answer to using your Canadian PPL on return to the UK;
FAQ Answer | Personnel Licensing | Safety Regulation
...and here for converting it to a JAA PPL;
FAQ Answer | Personnel Licensing | Safety Regulation
This is the situation at the moment, when you get back in 2013 we will be being regulated by EASA, so there may be some differences then.