I’ve had a lot of issues with my JER license whilst in London (insisted it wasn’t valid and only a uk d/l or international passport was acceptable).

I just got off JER-LHR and went thru T5 flight connections for a flight to EDI, and they directed me to a passport check (the “uk/Jer/Scotland” queue) and when I questioned why I needed a passport the woman gave me a clueless stare. I asked if a d/l was acceptable and she had no idea. Luckily I packed my passport but otherwise I’d have had to exit and re enter (even though coming from the CTA shouldn’t have been an issue). Who knows what they’re doing.