Ask an Property Solicitor. Get an Answer ASAP.
What do you want to know about this?
Why are you reluctant or unwilling to let the surveyor see the paperwork regarding your own loft conversion?
What are you looking to achieve?
Is your new wall which they want to use built up to the line of junction or does it straddle the boundary?
If it straddles the boundary, did you serve party wall act notice and get consent for this wall?