QUOTE(rbisset @ Aug 9 2007, 11:10 PM)

The Lonely Planet Europe give an example budget for UK as £20-40 ($40-80) per day but I think it's wildly wrong. I actually think it would be impossible for a traveller to live for a day on £20 in London unless they slept on the street and walked everywhere. Factor in £15-30 for a hostel, £5+ for an underground travelcard and it soon mounts up.
I haven't seen many places in Europe (planning to make up for that now!) but I'd recommend looking further than just the main capital cities. For example Interlaken, Switzerland sounds like a backpackers mecca! There is normally a small non-descript town in each country that backpackers make their home

Another example would be Cesky Krumlov, Czech Republic.
So far as travelling in London is concerned if you stay for a week or so, get a weekly travel card for the London Undergound, it works out cheaper than buying them each day! Definitely do the historical sites, Tower of London etc. I put a list on the UK forum for sights and stuff that are free in London. Try and get a pic of the famous Abbey Road crossing from the Beatles' days! I also think you would need to budget more than $40-80 per day in London, may be double that depending on where you are going that day, and add a bit more if you go on a longer trip!
Definitely try and add a trip to Czech Rep. if you can also, I agree its worth a visit!