It works on the MasterCard brand same as my Post Office credit card. MasterCard is widely accepted, I use mine (credit card) upto 10-12 times a day, never been refused anywhere.
I prefer a credit card myself, make sure you are aware of any fees involved https://www.fairfx.com/faq then click on charges.
The only problem we have had is when we first tried using it - the card kept being refused, but we discovered that the transaction needs to go through as a credit card rather than a debit card. Also the case with some ATMs - as long as you remember this you should be ok.