I would say you could get by on 35k but you wouldn't have much left over. Could do it for a year or two in a grind if you really had to though. Anything less and you will probably get pissed off with yourself as you will most likely feel under valued quite quickly. Especially if you have to pay anything at all for travel.
I was paying £250 a week rent for a one bedroom flat in a complex with gym + pool in zone 2.
Rent prices are a little higher than they were two years ago now though!
In the summer I used to walk which took around 40 minutes so I spent a little less.
Myself, my wife, 3 children, a car in a 2 bedroom maisonette with two gardens in zone 5.
No problems. Apart from the incurred debt from having to live on a much lower salary for several years beforehand. That is the biggest problem for me.
I live in Zone 4 in a 1 bedroom flat for £910 a month and I only earn £42k.