Just got mine at Marks & Spencer Foreign Exchange who don't charge any commission, I got $1.56 to the £ today.
Took cash out of the building society and so avoided paying any charges there as well.
I've used the Post Office in the past as well who don't charge commission, but you have to wait a day or two to get the money, at M&S they had it all in stock.
HTH
Astrid