On Tuesday, November 27, 2012 1:32:45 PM UTC, tim..... wrote:
You are obliged to enter into a party wall agreement with him This should be drawn up in a way that protects all of your interests, though I can't see that underpinning is one of them.

But they want to build a wall (with 1000mm+ foundations presumably) right next to the OP's wall which, being victorian, probably has no foundations at all. I think there is every chance that the PWA should specify underpinning. It can also require that no load be put on the existign wall - i.e. their structure must be self supporting.

IANAL
Robert