Use a foreign exchange specilaist bank. These banks heve GREAT exchange rates (just off the interbank spot rate) and charge no commission or fee.
They will handle the exchange rate and the transfer - I would definitely exchange the $ into �.
You can set it up and have the transfer done in 1 day if you provide the info fast.
Here is a list ofsome UK Foreign exchange banks -
http://www.whichwaytopay.com/compare-foreign-e xchange-summary.asp
I used world first - good service, good rate.