I've sold to many PO addresses here in the UK, from buyers abroad, as I have no international posting, so it's a way for those buyers to buy from UK sellers.
If the address is there on ther Paypal address it's fine, you can also Google Map it, to confirm that address is valid, give you more confidence to post the item.
Is it valuable? Add the necvessary tracking and insurance if it is.
Do advise your buyer as obviously there are so few flights from the UK to the US, their item may take a very long time to arrive.
