And it's not ideal of course, but you could always have the money transferred to his/your US account
Yes this, and if you're not familiar with FX transfers - check a few sites for their fees and exchange rate before moving the money. And do a small transfer first if it's a large sum to make sure you haven't made any typos etc. I've had the most luck with transferwise, but there are some others that are good for larger amounts (check the money matters section). Bank rates are rarely the best deal, but it's worth checking those too.
I have a feeling with brexit the value of GBP will drop closer to the dollar, so that may also help! You'll want to keep an eye on the Oanda exchange rate as you get closer to submitting, as that value the day you submit is how they calculate if you have £62500 in savings.