51attack, We do accept US clients, whilst there is no UK tax issues when you sell the wine (VAT, duty, capital gains tax) I can't give you a firm answer on what tax implications have been triggered (if any) when you convert Bitcoin to wine. Every country has different views on the matter.
The reason why I was asking, is that if you are providing a return on someone investing, there maybe some legalities with the SEC. Even if you are in the UK, if you accept US customers, the US could still knock on your door.
Similar to the way ICOs are locking out United states citizens. Because they fear repercussions.
I think the idea of investing in wine using the blockchain is very interesting and doable. I know there are those gold backed cryptos.