I used a company called Currencies Direct for transfers to Germany and the USA. Rates as good as I could find and no extra transaction charges, except that the seller's bank in Germany deducted quite a big charge for receiving the money which was already in Euros! (I believe that this charge was later refunded when the sellers of my boat complained)
My own bank in the USA charged me just their standard $20 for receiving a telegraphic transfer.
I've used Interchange FX in London, do a google on the net and have a look. All done by telephone backed up by email/fax. Good exchange rates and very easy people to deal with. I've used them on several occasions this year and they have been flawless.
Dave
Try hifx.com - I used them and would do so again. Very sharp rates and none of the heavy charges imposed by the high street banks. If you are not too time pressed, set a target rate with them and try to let them achieve it - that's the way I did it, over about a 3 week period.
Likewise you can buy ahead and fix a rate if you think the GB£:EURO is going to deteriorate.
It's a competitive field with many specialist currency shifters. You usually need to register with them first, sending the usual money-laundering proof of existence - bills with our address on etc, but once that's done, the process is easy, and can all be done by phone with fax confirmation (after the event even once they're used to you).
Rates vary by amount being transferred and company doing the transfer, so get booked in with two or three, and ask for quotes. Last time I did this (only for €11,000) I was quoted 1.43 to 1.46 exchange rate, usually with only £10 additional charges. That's for an interbank transfer using IBAN. A currency withdrawal from a local bank will be more expensive.
My last two transfers were made by currencies4less , but I've used others. Beware, the published web rate most of them show is a lot more favourable than the real life quote you'll get!
Especially if you're considering spending much time abroad, it may pay you to open a Euro bank account with an international bank - HSBC or Citibank. Or choose a big national bank.