I am in the £20k to £30 bracket, and live very comfortably. Mind you, I live in a 3-bed flat sharing a room with my fiance, so our rent is stupidly cheap (a touch over £500 a month between us).

Renting a 1-bed flat or a studio will be very expensive, I'm afraid. Someone else has already mentioned a flat-share, and I would recommend this: rent will be cheaper, and you'll have a ready-made social life (hopefully, assuming you get decent flatmates) whilst you find your feet.

If you go for zone 2 in South London, rent isn't too bad, and you can easily walk/cycle to work: I live in Oval/Camberwell, and it would take me about 30 to 40 mins to walk to Southwark Bridge. If you could find somewhere around Borough/Great Dover Street, you're very close indeed (and close to Borough Market, omnomnom).

Travelcard: if you buy an annual one, it's just under £1100 for zones 1 and 2. You can probably get your company to buy it for you, and then you pay them back (I believe tax-free, but not sure about this).
(The Empress it seems you CAN polish a turd!, Tue 24 Nov 2009, 16:33, Reply)