I have emailed the CAA to ask them if I have paid up.
This FE did know I am flying on my FAA CPL/IR and I am keeping the UK PPL valid just as an anti-EASA insurance policy. He is very decent and I am sure he would have said something if it was important.
Is there any record anywhere on the license indicating the 5-yearly payment was made i.e. do the CAA send you a receipt, or can the FE check it online?