Very useful thread - thank you to the OP for raising and others for response.
This answers a lot of questions for me - my wife and I are taking our child (who by then will be 8 months old) to YYZ in June to visit Grandparents. We are travelling all together outbound but on the return I will travel back alone and my wife will stay 2 weeks extra with the baby before returning to the UK.
I therefore anticipate that some sort of letter may be useful a) in boarding the aircraft in YYZ and b) at immigration in MAN upon return to the UK. The examples on here are primarily US / Canada based - can anyone point to a UK centric version or advise any sample wording they may have used in the past (or give ideas of what we should include).
Thanks.