I've accepted an offer on my flat and am totally gobsmacked by how high it is. It's 235% of what I paid in 2005. Buyers have a 25% deposit. If the survey downvalues the property, how far below will it need to be to put the kibosh on it? I realise that the tenants income % will have an effect too.
as far as I know this will largely be between you and your buyers- if the valuation is below what they offered and they wish to keep the deposit at 25% they might ask you to lower the price. If they are happy and able to have a smaller % deposit then that is up to them.
Most lenders want at least 10% for the deposit so as long as they still have enough for 10% after accounting for the extra they will have to pay to make up for the difference between the survey value and the agreed price they can go ahead.