Change/update the contract during the fixed term

A deed of surrender is a real time process.
It is in effect once it is signed.

The only option would be that you do not sign if the property is not returned in the condition it was given to them.
I have used them in hostile situations so my solicitor has said stop worrying about what the condition of the property looks like as you are getting your property back. He always reminds me to look at the bigger picture!
The other option is you just don’t sign the surrender, but then you risk dragging the process out.
The tenant cannot afford the property and you need it back to let out again asap so you are not losing revenue.
In reality terms of the surrender need to be met before it is signed (we ask for the deposit -the tenant releases it before hand- and a months rent as compensation for releasing the tenant from the contract.)
My solicitor drafts the deed and we pass the cost onto the tenant in advance of the surrender as part of the terms ( that is written in an email ).