From what I know you can open an USD account at HSBC or Citibank UK, but you will have to contact them directly and ask for their fees and stuff as I was told they do have some.
I am not sure how much of a loss the exchange rate is, but if it’s a 3-4 digit number each month, will add up in time. And if there’s a simple solution like opening such account I’d say go for it. If it’s however very complicated, requires fees and your time or perhaps flying out of the country and stuff, I will just say let it be as it is.
Regards