Remember, you may get charged VAT and a handling charge if you buy from the US.
I was.
There's a supplier in the UK - I can check but it was easy to Google - somewhere in the South West who suppliedmy Mobil 1 V Twin. 6 quarts for about £90, which is an awful lot of money.
The Harley V Twin synthetic oil is (probably) similar, is cheaper and easier to get hold of.