No need for a car and unless you must live on your own, rent's not that expensive either. As CF alludes, living more central can work out better – you can save a fair bit on travelcards so you can afford to pay slightly more for accomodation.
My rent is still £475/month in zone 2, inc council tax and TV licence – my gf and I rent two rooms between us in a shared place. Little bit more for bills. Zone 1-2 travelcard is just under £100 a month, or cycle everywhere instead. Food £100-120/month if you're living economically and taking your own lunch each day. Add a fairly generous £200/month for everything else – entertainment, booze, clothes, bike bits. That's about a grand a month, for which you'd need to earn a salary of about £16.2k. Forego the travelcard and cycle everywhere and that's more like £900/month, or a £14.7k salary needed.
Obviously the more you earn, the more comfortably you can live and afford new bikes, holidays, gym memberships, sandwiches from pret for lunch, posh coffees and all that other stuff.