MT1234567 - wow what an amazing coincidence that would be.
Sounds like a bunch of sharks to me. Contact Which and Watchdog as well as trading standards. Probably worth contacting Canon UK as well - under the circumstances I expect they might be willing to help - possibly even issue you with a UK warrantee as you have acted in good faith.
This sort of thing is bad for their reputations so they might be willing to throw a bit of muscle behind it.