Do you get a letter in the post if you get a very high UMS overall?

Nada. I'd imagine most schools with a decent maths department each have a bunch of students getting 590+.

You might get one from your mum....

You need to recalibrate your imagination then.

Really? I attended a averagely decent Grammar and there were at least 8 students with 590+. I didn't think we were that outstanding.

Really? I attended an averagely decent Grammar and there were at least 6 students with 590+. I didn't think we were that outstanding.

There are twenty times as many state maintained secondary schools as grammar schools in England and Wales. Your experience is not typical.

Clearly my experience is not typical but the number of Grammar schools is over a hundred and combined with private schools, that would put the number of students obtaining 590+ well into the hundreds, and as such way too many to be sending letters of achievement to everyone of them.

I fear you may be overestimating based on your personal experience but have no figures with which to back up my hunch. You are quite right in pointing out that the number would be too great to reward with individual letters.

I'd guess the number of students getting 1180+ in M+FM would still be non-trivial (perhaps in the hundreds)

Probably not. Most students capable of achieving that would have secured a Cambridge offer but Cambridge only has 240 (is that right?) places. I suppose it is plausible that 100 applicants would have 1180+ but it is probably a low three figure number if indeed it is in three figures at all.