If one user beats the interbank rate, that implies that the other side of the trade lost out. The same number of customers who 'beat the market' also lose out by definition, so I think that's something to be wary of marketing.

In any case, my 1% assertion seems to be correct judging by a €600 purchase compared against FairPay (£513.73 rather than £519.26).

Incidentally, is your name inspired by Betfair?