Gas Safe Engineer doing a foreigner - what should I ask?

[EvilDrPorkChop]

Depends on when you started. I joined CORGI when it first became mandatory, in about 1990, so have a 5 digit number. Cost was fairly minimal IIRC

Don't see so many 5 digit numbers these days...ours is 5 too 😛 Not entirely sure when we joined though.