Smell when Potterton Suprima 50 boiler shuts down

[michin]

I am experiencing a foul smell (difficult to identify, but not burning or gas) in the kitchen, which is prominent only after the central heating has been in operation, and the boiler has shut down.
I live in a modern house (built c.2001) and the boiler, a Potterton Suprima 50, is fixed to an outside wall in the kitchen. We cannot determine exactly where the smell originates, but have eliminated the dishwasher, sink and washing machine waste outlets as possible causes.
The boiler was checked over by a CORGI engineer, who was told about the smell, but no problems were found.
Any ideas?

 

[buck51]

thats a difficult one, but can you remove the plinths from kitchen units, and check their are no dead mice etc,

 

[grahamderek]

more to the point, check on top of the boiler