I’m a Londoner and moved up to Edinburgh, Christ, is it really 9 years ago. Move was to follow a bonnie lass whom I am now married to. Personally I find the quality of life up here far better than London.
I used to live in North London, edge of zone 2/3, and rental for a nice-ish two bed will be between £1,500 and £2,000. Your commute to the City would be 45 mins to an hour door to door. A similar flat in Edinburgh would be - guessing here - £600. You could rent a 5 bed house for £1,500 (we did when we were house hunting)…
London is certainly more fun if you are young but Edinburgh has everything you are looking for in a small capital city, great buses which everyone uses (really no need for a car in the city centre) and a great restaurant scene. as well as museums. Personally as an outsider I find Edinburgh easier to get on with than Glasgow and as a finance professional it is just as good job wise (for every other job you would be better off in Glasgow as more than twice the size). Edinburgh regularly wins best quality of live in UK city surveys.
Permanent jobs are tricky right now in Banking - at least in senior grades - but lots of fixed term contracts around for £300/day+. There are also strong fund management and life insurance sectors, not really any general insurance jobs (that is more Glasgow). Edinburgh is something like the 5th biggest financial centre in Europe - second or third in the UK
Happy for you to PM me if you want more help - we share a strong interest in military history for a start. Best of luck with the move!