Yes. The smell is coming from one of the drains. Once it's blocked off or had bleach down it the smell will go.
OK Joe I shall take the plumbing out and leave it outside for the night and block every orrifice in the kitchen?(obviously not use the sink etc) and see if the smell subsides and some bleach.
If this works Beers are en route.
Just please confirm.
Cheers,
Chris