José M spanisg atorney.
I can advice you about to how to go out of the fractional membership contract, according to spanish law, but no about the finance contract you got in UK according UK law.
Once you know that, your rights about to declare nule the spanish contract, will be found at the 11 Article of the law and the colling period at 12.
Be sure that you got a legal writting contract with alll the requirments said at 11 and be sure they give you the colling period of 12. If they miss you will be freee to declare the contract nule.
But I am sorry to say that even you got it nule, the finace contract in UK could be legal, so you have to manage it with a UK barrister to find an exit of it
Even you could sue the company here in Spain but you will have to pay the financial contract in UK
So, read carefully the articles 11 and 12 of the spanish law 4/2012 and check if they miss your rights in order to declare your contract nule
I will be here if needed, thank you
LINK to the law in english