the time has come when I've been asked to get the house valued. I am considering asking for a valuation based on a 'forced sale'. Is that okay? And at what point during the discussion should I inform estate agent / surveyor that that is what I looking for?
Yes, it's generally accepted in the Insonvency world that a valuation be based on " 3 month forced sale basis". This is roughly 10% less than market value.