Here's the official answer:
https://publicapps.caa.co.uk/docs/33...ice2017034.pdf
If you are renewing your SE/IR, you'll need a bit of training and a skill test, obviously. If you do that in a GNSS equipped aeroplane, generally it gets picked up and annotated onto the paperwork as part of the training and examination process. I recently converted my FAA SE/IR into an EASA SE/IR, with a bit of groundschool, a bit of sim time and a bit more airborne time, both with a GNS430 (or simulated equivalent) in the cockpit, which picked it all up, and the paperwork went into the CAA with "PBN passed" annotated on it by the examiner.
G