Try a bidding site

Opaque rates can save you up to 60% if you book a bit blindly

Opaque rates on lodging allows you to save significantly so long as you are willing to wait on learning all the details until after you've committed to pay for the hotel.

You are only given the prices, neighborhoods, and star ratings of the properties (a few dozen in big city like London, a handful to a half dozen in a smaller town like Oxford or Bath).

The actual name and address of the hotel doesn't come until after you've given them your credit card info and paid for it—but the savings can be huge. Take the results of this recent random search I performed:

Hotwire's "hot rates" offered double rooms in central London as follows:

• Five-star hotels from $187
• Four-star hotels from $73
• Three-star hotels from $40

Priceline's "Express Deals" had these rates on double room in London:

• Five-star hotels from $195
• Four-star hotels from $87
• Four-star condo from $64
• Three-star hotels from $59