Originally Posted by UKtravelbear

There is more to sponsorship than just a contract for the musician to perform. It means you must meet certain legal obligations and there can be legal repercussions if you break them - not just for you but the artist.

I suggest you find a UK immigration lawyer as this is a fairly specialised area or contact a concert promoter in the UK as you are in the same business.

Is there not a professional association you are a member of you could ask?