Thats's not a bad idea. Cheers. Vendor is a good friend so I doubt there will be an issue with this. Besides, he owes me a couple of grand for something else :D
I've seen it done on numerous occasions - unless the vendor is a really good friend then I'd keep it all as official as possible, purely for peace of mind and all that business.
In that case, offer to rent it until you actually complete.
Fairly common thing to do. You've exchanged contracts, so unless there's a modern miracle you're legally bound to complete.