Subsidence!

Have had an offer accepted on a property - 1930s semi. Needs quite a bit of work, but managed to get a good price (15k off asking price). House is unoccupied as the ownder has died. There is a big crack in the wall, which the daughter has apparently told the EA has been there as long as she can remember, I was also told they had supposedly had it checked out and it was nothing to worry about.

Had my survey last week, surveyor reckons its more recent movement, quite possibly caused by a damaged gully running alongside one corner of the property. Still waiting for his report, but he's told me we need a structural surveyor to check it out. He reckons it might only need to have the gully excavated and renewed, and a concrete support placed alongside the foundations (although we won't know until the site is excavated, worst case scenario is underpinning might be required). He reckons we need to go back to the vendor once we have the surveys/estimates to re-negotiate the price. I don't know if they'll budge though, as the EA was quite surprised they accepted my offer last time. Surveyor reckons we are in a strong position, as if they reject our offer and we walk away, any future prospective buyers will also find out about subsidence etc.

I'm aware that a history of subsidence might make the property more difficult to insure. Surveyor reckons this shouldn't be the case, as we will have all the surveys etc to prove what was wrong, and what was corrected. He also reckons it shouldn't impact any future sale price. I am worried about getting a mortgage for it though.

Anyone offer any advice/tips? Anyone been in this situation?

Cheers

-D