I was looking at some of the budget hotels in London on Tripadvisor.com last night, and their prices were higher than what I've got on priceline in the last, or booking directly with Thistle hotels with some of their promotions. Travelodge also has some London area properties for 26 pounds a night (about $46) for selected dates.
http://p070.ezboard.com/bpricelineandexpediabidding
http://www.betterbidding.com/
http://www.thistlehotels.com/
http://www.travelodge.co.uk/