Hostels - Booking online might save money, but not much.
Advantage is you're sure of a bed for the night.
Downside is you're committing yourself to a certain itinerary.
Public Transportation:
Trains - VERY VERY expensive if you don't book in advance, so if you know your dates and times and are confident about making the right date and time, do it.
E.g. B'ham to London booked a month in advance - about £20. Pay on the day - over £100.
Probably best to avoid trains (Compared to Germany, they're slow, dirty, unreliable and stupidly expensive)
Cheapest way (between major towns) is Coaches -
National Express are cheap and reliable.
Within London - buy a day saver ticket for all trains,underground trains and buses (A 3-day central London is £17.40, £40 for Greater London))
For London Travel, check out
Transport for London.
In London, even cheaper is to order an
Oystercard (prepaid swipe card) that saves a lot of money if you can plan ahead.
Edit : forgot Maps
Lots of people will try to sell you maps! There are also vending machines. As in most countries, find a Tourist Information centre (most airports and major ports & railway stations) and the maps are free, and the advisors can usually give you specific information about where to go.
Again, PM me if you need any specific information and I can always email or mail stuff.
Another edit: Link to Youth Hostels Association - Very good value - between £10 and £30 a night)
Edited, Nov 2nd 2008 11:27am by Nobby