Re: UK suit against US resident

I cannot answer as to whether he can sue you in the UK -- you would have to ask a UK solicitor that question. However, if the purchaser has a valid claim, he can sue you for breach of contract or tort in the USA (and possibly in Spain - check with a Spanish attorney) wherever he can get personal jurisdiction over you -- i.e., where you live.

If he can sue you in the UK, and somehow can serve you with the proper court papers under the Hague Convention, he may be able to get a judgment against you in the UK and have it recognized by the Courts in the US. Again, you should check with a lawyer/solicitor in the UK to determine whether you can be sued there.

Re: UK suit against US resident

He can sue you, though without more information I can't say where such a suit would be proper. A lawsuit in a British court would probably be appropriate, but he might also be able to sue you in the U.S. or Spain if he wants.

Nothing you have said sheds any light on how likely the buyer's suit would be to succeed. If he eventually gets a judgment against you in any of the three countries you mentioned he will probably be able to enforce it against you in any of the others. Doing so will be costly and time-consuming, but it will be possible -- and you may end up having to pay the cost.

The title of your post suggests the lawsuit will be in the UK. You should consult with a barrister or solicitor in the city where the suit will probably be filed.