I would like to say a couple of website I use are:

You May have seen a guy on ITV called Martin Lewis, this is his site:
http://www.moneysavingexpert.com/

and a very popular forums:
http://forums.moneysavingexpert.com/

Don't forget to subscribe to his newsletter, over 1 million people do.

Another very good site is:

http://www.hotukdeals.com/

Has daily hot deals and a great voucher section.

Before you buy anything online! Go here:
http://www.quidco.com/

Quidco is the web's cashback cooperative. Quidco collects referral commissions from online merchants and passes them all on to our members. The Quidco cooperative is a cashback revolution where members keep their full earnings in exchange for giving Quidco £5 out of their earnings once a year.

The Quidco model works for both the merchant and you. It enables the merchant to reach a large _base_ of motivated savvy buyers and it enables you to get back big savings by buying from merchants who participate in the model.