Have used TCB and Quidco. Quidco charge you an annual fee whereas TCB pay you the full cashback and increase it the more you use them. So usually TCB are better than Quidco. When it comes to failed cashback tracking, TCB seem better at getting you your cashback. They also will pay out when you want it, not on a fixed payout date. Haven't come across a better cashback site yet. Though still have to wait months to get paid out. The industry itself is fraught with loopholes and failures (see this article: http://www.guardian.co.uk/money/blog/2011/nov/03/cashback-sites-consumer-rights-minefield ) but TCB seem to be the leader.
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