The registered mail trick is oft heard, but it's also something that can get shot down if it comes down to contesting in court.
I can't speak for the Canadian, UK or other copyright requirements, but for the US at least, if you're recording and selling your work and copyright is a real concern... do it right. It's not that hard of a process, and if you really want to protect yourself, going the full distance is a MUCH better idea than relying on something a lawyer can shred in thirty seconds in a court.
M