He's not demanding £13k though, he's entitled to £13k because he has a contract with Wolves where the 2 parties have agreed for the period of that contract he will be paid £13k per week.
If BHA decide that they want a further loan of the player his contract still needs to be adhered to.
If he...
He will be paid £13k next Season whatever happens!
He played for us last Season, we paid him £10k, Wolves paid him the other £3k.
It's up to Wolves, not the player.