I use Quidco and TopCashback, I've claimed nearly £1000 in cashback over the past couple of years, they are brilliant! Here are my referral codes
Quidco: app.quidco.com/raf/bNK6
Here's my referral link for TopCashback www.topcashback.co.uk/ref/Joamywharton/?source=App-iOS-TAFPage