The other thing to watch out for is if the anti-fraud measures at your credit card company trigger an alert.

I've been told a few times that small value transactions are sometimes used by criminals to test card details. If the payment doesn't work (perhaps because the card has already been reported stolen) then they abandon that one. If it does work, then they can try larger amounts.

Some card companies will suspend or even cancel your card if they suspect fraudulent transactions, which can obviously cause you all kinds of grief. Others will simply phone you straight away, "take you through security" and ask if that 1p you spent on RingGo was actually your transaction or not.

Obviously, be very careful to ensure that the card company that calls you is actually your card company - and not a fraudster.