Are you sure? you can't pull extra money out, like you can when it has a credit or debit attached to it, so say if A gave B ten dollars, B could then go and buy something off ebay for 7 dollars or what ever (as long as it was under 10 dollars) that's what I but then if JB Lee says he 100% knows it then I'd go with that and to make sure test it with said 50p, and now it's down to 2.5DOLLARS because the British are awesome that translates across to about... do doo doo do doo... 1.25 pounds...
Hope this helps,
- Nick