You, need to cash it or pay it into an account in case they change their minds.

If you don't have a sterling or multi-currency account, I really would suggest finding a way of keeping it "safe" in £'s until the exchange rate is better - unless of course you really need the extra, even if it means "losing" a little bit because of a weak £.
[I could look after it for you, in a nice little offshore a/c, until times/rates become better

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