Has anyone used TopCashBack.co.uk to get money back on their online purchases?

Has anyone else on this site ever heard of or used TopCashBack.co.uk to claim back cash when buying stuff over the internet, this site was recommended to me by someone on “moneysavingexpert.com” although you can request payment by cheque they will only send a cheque when you save over £75, you can request payment into your bank account for any amount but as you would need to supply them with your bank account details In order for them to send you cash back on your purchases I am understandably wary – for one of my purchases I will be sent £40 back so I am eager to use their services but only if I am sure they are legit, so has anyone else in Britain had experience of them.