This might be useful if you are going to shop at Amazon anyway, and want to try and find a bargain.
www.discountselector.co.uk lets you try and find what you're looking for at a discounted rate (e.g. 10% off, 20% off, 50% off etc).
You pick how much discount you're looking for, enter what you're trying to find, and it takes you to Amazon and shows things that match the search term with that amount of discount.
Certainly doesn't work every time (not everything is offered with money off) but certainly no harm in having a look first when you're looking anyway, and is very simple to use! 