As far as I am aware you can use a Canadian PPL to fly in the UK Day VFR only.
I am a UK citizen but I work in Canada on a Canadian CPL/ME/IR land and sea.
I have written my CAA ATPL exams but I still have to do a flight test for conversion.
Contact Nic Denson at Leeds flying School,UK. He is pretty clued up on this stuff, that is where I am going when I get home.