I am leaving for the states in around a months time and upon arrival I will be opening a US account. I'm a student and so will be sending around £2,500 each term to the US account from funds that are paid into my UK account. What is the most efficient away to transfer this to my US account without losing a lot in the exchange?
My current favorite service for this kind of transfer is Transferwise.
The fees are quite low when compared to the 2.5-3% by high-street banks for currency conversion, to which you need to add the international wire transfer fee, and it's often a lot faster, as they split it into two domestic transfers while the international part + currency conversion happens internally to Transferwise.
If you set up two Paypal accounts (one linked to your UK bank account and one to your US bank account and get them both properly verified) you should be able to transfer the money for free as far as I know.
You would have to fund the transfer directly from your UK bank account (not via a credit card).