[vinylweatherman]

In the above case a player is being paid in GBP, so surely they would want to play in the currency they have available. This is not playing the "pound edge", and should not be penalised. Playing the "pound edge" would be depositing from a dollar bank/card account but playing in GBP and taking the currency conversion hit as a cost of taking a GBP bonus.
This fee should not be "buried" either, this player should have been informed up front by CS before he played so that he could change his mind about playing. The internet has no borders, so why should it matter if a player works long term away from his own country and wants to play online while doing so. he would find it very hard to use a US bank or card anyway, as they don't allow casino transactions so I see using his GBP accounts as the only way.
I play in GBP, not because of the "pound edge", but because I would suffer erosion each time I deposited and withdrew due to currency exchange fees that most bakns and cards, and even Neteller, charge. These could actually approach the 5% level.

A better term would be to state that players in GBP must deposit from an account (bank, card, Neteller) that is itself denominated in GBP. This will stop the bonus players, but would not catch out those with "unusual" working circumstances. People working away from home are probably good customers to encourage, as they are probably away from family and friends, and have more leisure time to spend on such solitary activity. They are also probably wealthier than most, as the main reason people work away from home is a better salary, or being in a senior position (with expenses for working away to match).

Perhaps one day the UK will adopt the Euro, and all this will go away.