Hi Jon,
I expected to be told that you can close one account and open a new one in pounds, but you cannot have a second first deposit bonus. However, I have just checked with the Casino team and yes, you can indeed claim the first deposit bonus again.
You must however, as we have all said, close your old account first and liase with customer service via chat or mail. Also, this is important for any affiliates here and I know there are many. The affiliate link/tag will be transferred when the new account is opened, this is part of the reason this has to be done manually.
Good luck!