Last minute hosting change cost

I have built a Wordpress site for a client. It is all built and ready to go but I still have the under construction page up.
It is in the contract that I will host the site, and it was one of the first questions I asked them.
However they have suddenly decided they want to host with someone else. I have not been paid at all, so I am not transferring the hosting until I have been paid for the work.
My question is, would you allow them to change the hosting at this stage, and how much would you charge (£) for the work of transferring the hosting?

It depends on what you’d normally charge someone if they asked how much to host the same?

Equally, what you’ve quoted them as a total fee.

Depends if they’re overdue with payment, or if there has been other signals that might indicate they’re not going to pay. I always have a line in the contract that stipulates all code remains my property until payment is made in full, and isn’t transferable until then.

Rule #1, setup a payment schedule up front. I personally require at least 50% upfront, then depending how long the project is, may require another 25% at the 50%/75% completion mark, and finally the remainder before any goods are transferred.

Charge what it would cost you at your hourly rate to transfer the site to a new host, setup any databases, etc. Estimate the best you can and then tack on 10% for unknown cost (that is what I do).

Same here.