I was in the same position. Did my Class 2 just before the rules changed (mine was issued with a VCL restriction because I failed the stupid feckin colour dot test). A while later I passed the colour tests and they sent me a new unrestricted medical. Whaddya know, they'd retrospectively applied the new validity period to it and it was now valid for an extra 3 years!
Might be worth giving them a bell and asking?