I already have a Mortgage Valuation report....

Even if you are seeking a mortgage and may be paying for a Mortgage Valuation report it is still advisable and prudent to arrange a survey by your own surveyor. The Consumers' Association Which magazine and the Council of Mortgage Lenders both give this advice.

The reason is simple: the Mortgage Valuation report is prepared for the lender not for you, the borrower. It answers only the lender's questions concerning the appropriate security for your loan. You cannot rely on it to answer the questions, which concern your personal interests.