Hey Nick!
I'm 23 and have lived just slightly outside London for almost 2 months.
I love life here but will be heading back to Canada in January as I cannot get a job here. I am on the YMS visa.
For visa information, check out the
UK Border Agency website. That will give you all the information you will need on the different visas, how to apply, etc.
As for money, I would budget like this:
Start up costs:
-YMS application fee - $314
-budget for living in a hostel for 1 month - $40/night-ish+
-budget for
flight (this all depends...my 1-way ticket with Icelandair was $527 with tax)
-budget for checking extra luggage
-budget for food - I can get away with approx. £35/week
-budget for things that you can't take (for girls, this would include things like mirrors, hair dryer, straightener, etc. Lol)
Living costs:
This all depends on your situation. I got lucky and am staying with a friend of a friend for £350/month. Nobody will rent you a flatshare without meeting you first - and be prepared to be turned down if you don't have a job. Also budget for nights out - easily done in London LOL!!
For me, I've ended up spending approx $1000/mnth to live and do everything. Check out gumtree or spareroom to get an idea of rent costs. Different boroughs will be priced differently (they also all have a different feel to them).