A mortgage valuation protects the lender, not the buyer — it does not assess condition. A RICS survey is the buyer's own due diligence. Level 2 suits conventional, reasonably modern homes; Level 3 is for older, larger, altered or unusual properties and reports in depth on defects, causes and repairs.
The survey can change a deal: it flags structural movement, damp, roof and services issues, and often gives a market-value opinion and reinstatement (rebuild) figure for insurance. Findings are routinely used to renegotiate price or require works before exchange.
For prime and listed stock a Level 3 by a surveyor experienced in that building type is the norm. Book it after an offer is agreed but before exchange, so there is time to act on what it finds.