Thanks for the info from all.
I have a friend who had company loss of licence insurance, had a heart attack and got £80k which was on a salary of about £30k at the time. I'm ex-NATS and vaguely remember their terms as being something like 4x salary (a fortune on NATS salaries!).
I'll post any updates in case it helps anyone else trying, but sadly they seem to be slow in coming... another 2 emails sent and still no response. Any further info, especially advice on further companies to try and/or how much private punters pay for their own insurance, would be gratefully appreciated!