Why complicate it? When SS is deposited into a UK bank account, it goes in without fees and at the best exchange rate. Over the course of a year, you won't really 'lose out' - if it's deposited in a US bank account, any transfers to the UK will need to be done from the US, will involve fees, and you're still at the mercy of the exchange rate in effect at the time of transfer.
Our SS goes into our UK account promptly on the 3rd of each month. Some months it's a little more, some months a little less, but over a year, there's not much 'gain' or 'loss'. Plus, it makes it far easier to file the UK self assessment, which no need to figure out exchange rates.