I'd be grateful for any advice or experience as I dither about what to do.
Varnishing existing floorboards is a lot cheaper, and arguably looks better. However, I can't help but think it is unhygenic as dirt accumulates between the boards, and the floor is harder to clean, and not as comfortable to sit on. When the house next door had it done, the fumes from the varnish made our house unbearable for nearly a week, and that is putting me off more than anything.
Otherwise we could put in a wooden floor, which would inevitably cause us grief when it gets scratched/stained, and will probably look dated as fashions change. We are hoping to build an extension in a couple of years, so the floor would probably have to be uniclic or similar, so it could be lifted and moved. It is so expensive, and seems silly, given that there are wooden floor boards there already. But it would be easier to clean, and provide better insulation...