Been under offer for several weeks - drains starting to smell

[duro1]

Do I have to declare? They are not having a survey??!! I am single parent struggling, they have couple of other properties... I know that probably doesn't matter but it does to me ie. can't afford any problems

Where is the smell coming from? The plugholes in the house? The manhole cover outside?
Powerful drain unblocker really isn't expensive and works very well on blocked plugholes.

Can you pull up some drain covers and have a look?

My drains smelled after house had been empty for a few weeks. Disappeared with use- could it be that?
Water and bleach down all drains - we have a cesspit so can't do that