To add to what Simon has said - it also depends upon what kind of survey you had done. A valuation survey is *not* a survey which looks at the structure in anything like the sort of detail required to *properly* check the structural condition of a property, especially an old one.
To put it bluntly, a valuation survey for a mortgage is really nothing more than a lender covering its backside to say that if you stopped paying the mortgage and the property is repossessed, is the lender likely to get its money back on a quick sale.
With any older property, as a person previously involved in the property market, I cannot stress enough the importance of getting a full structural survey done. Even more so than a housebuyers' survey which is the bastard offspring of a full structral and a valuation, and is neither one thing or another. A full structral costs serious spondooliks, but for an old property, it really is the only way to go.