Has anyone got any idea what this smell can be? My bathroom/utility is one large room. I live in a cottage over 200 years old and about 2 weeks ago I noticed an odour which has become so strong it makes me feel sick. It is definitely not from the loo and we have checked all manholes. We have checked bathpipes, drainage and water outlets. The utility area has a washing machine and small freeze and we have removed both items from the room. The smell is like a gas or corrosive sour smell and is definitely not a sewer smell and we are not on mains gas!
I can clear it when I open the window but it comes back also we have taken up bathroom floor tiles thinking it was maybe a fracture in the oil pipe under the floor as we have oil fired central heating but this is all dry. The smell is in one place one day, and somewhere else in the room another day and is nowhere else in the house - any suggestions anyone?

If it is not a sewer smell do you think you would recognize mold and mildew smells? 200 year old cottage can have lots of surprises in the plumbing.