I run a small startup in the UK (www.mycurrencytransfer.com) that helps people compare currency transfers from different providers.

We've found specialist currency brokers such as Moneycorp, The FX Firm, IFX, and World First, amongst others, offer more competitive rates than the banks.

They are what businesses tend to use when paying overseas suppliers, and people purchasing properties overseas.

(Sorry for the "shameful plug", I just thought I'd chime in seeing as it seemed appropriate)