DerbyBorn wrote:
Will be having some quotes soon for an extension. I am considering
asking the builders to supply their own toilet to avoid having ours
messed up. Any thoughts on the likely cost and how a builder may
react?

It doesn't matter what it will cost because the builder won't be paying for
it, you will.
The builder will probably be happy to have somewhere to have a **** without
waiting for you to go out so he can do it in your gulley or behind your
shed.