By using any credit card you will get close to the interbank rate - far closer than a money transfer. Most card issuers will charge you an exchange fee of 2.75% in addition. Despite this paying by credit card is still cheaper than a money transfer. Some card issuers (Nationwide, Post Office, possiblty Saga) waive this fee so you will save even more, but these issuers will not pay you Airline Miles etc. So...if you are looking to boost your airline miles balance you should simply use your credit card. If your limit is insufficient you can either pay in stages, or simply pay money into your credit card account so that it goes into credit and explain to your credit card issuer what you have done and why in order to prevent anti-fraud declines.