Thanks Olof. I've popped an e-mail over to them.
BigGrecian: The letter from the CAA I received with my medical certificate states that "CPL training must be completed in the UK; a certificate issued as a deviation is only valid on UK registered aircraft. If you wish to operate using JAA class 1 medical certificate privileges on aircraft registered outside the UK you would need to obtain special permission from the appropriate regulatory authority."
The wording in the last sentence in a little misleading. I've checked with them, and this only applies to training before the deviation is removed. Once the deviation is lifted, it will be a class 1 like any other.
And thanks WBV - it may not be an issue after all.
waterpau