Hi,
I'll try and answer this but the usual cavaet in checking with the CAA themselves applies as I could be wrong in my interpretation.
The wording of LASORS implies that if you had the IMC Rating issued on the basis of your JAA IR(A) Rating then you would be subject to the usual validity but it would expire after 12 months if you hadn't revalidated your JAA IR(A). If you kept your JAA IR(A) valid then the IMC would remain valid but after 25 months you would have to take an additional flight test with an examiner to revalidate your IMC Rating even though your JAA IR(A) remained current.
That you had the IMC Rating issued as a standalone rating not in conjunction and on the basis of validity with the your JAA IR(A) implies that the usual validity remains in force for your UK IMC (ie it expired on the 30th Jan) and even if you let your IR lapse your IMC rating will still be valid.
So your IMC rating doesn't lapse after twelve months if you let your IR lapse because your IMC Rating was/is a standalone rating issued before you even did your JAA IR(A) (but you have to revalidate your IMC Rating with an examiner).
Why you would want an IMC Rating as well as a JAA IR(A)? Well there are a few good reasons (such as still allowing you to fly in IMC except in Class A / Airways if your IR had lapsed) but these would only cover you in UK airspace.
I'm confused as well!!!
Best wishes,
Charlie Zulu.