I was in a similar position a couple of years ago and the rules may well have changed. Nonetheless, if your original JAA Licence was issued by the UK CAA, you should now be entitled to a UK Licence, which is non-expiring. There would be no valid Types Ratings on this licence. However, if you joined a new airline, you would do the conversion course for your new type. Conversely, if you were to continue on the same type e.g. A350, it would involve the Operator's Conversion Course. The Proficiency Check would put the A350/IR on your UK Licence. It may well have changed, but the likes of Jet2 and Virgin seem to understand what's involved.