I believe non-expiring c of a's will be issued on or after 28th Sept 2008. All c of a's leading up to that date will (should) be expiring on that date (at the latest) for the non-expiring ones to start.
(Only the CAA could try to do this - and we end-users wait to be proved wrong!)
By the way - if your next c of a can't be done by a Part 145 Subpart F/G Holder, the CAA will no doubt charge much more than you're used to. Time to get it sorted out.
Check the C of A document - I'm sure you'll find it has a UK reference number, not EASA Form 25 (or whatever)