Given the current rate is GBP/USD 1.5951 & GBP/EUR 1.1446, none of those seem very good.
Caxton is very wrong, the PO is offering $1.551 for example or was earlier ...
Whatever, I used Tesco, the rate was acceptable, I thought the service very good, and I had faith that it isn't a banking bubble and my money was safe (exchanging thousands makes me want this!).