This is between you and the buyer.
Send them a 'letter before action' using a tracked and signed delivery service.
If they agree to returning the hot tub, you will have to arrange to collect it.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
