It's not 7% though, because you are paying that over 3 monthly instalments. The effective annual rate would be (by my calculations, anyway) more like 55%.
Doesn't say that at all though. Says £7 upfront then 3 x £33.33 payments equaling £107 for a 3 month loan for £100 of goods.
If it is as straight forward as that then it isn't so bad. But there is probably something in there where for a £100 product you pay £7 up front and 3 monthly payments of £80.