Apparently, in the past, at my stage of development, one rang the CAA and said 'I've got 1,500 hours instructional and would like to become an examiner' and they sent back your approval in the post.
Almost, it was actually AOPA you rang and you needed the endorsement of a club/school.
the CAA think that 250 hours is adequate! How does that work?
I don't think they do; it's EASA who think 250 is adequate, so that you can exercise one of your civil rights no doubt; the CAA have no say in the matter.