They're not near Bath, they're actually in Bath! The longer of those two is just under a mile, I think. I've no idea whether it is the longest though.
As to the Queensbury Tunnel, it would be great, though: a) I understand there's no paths to/from each end (but I guess that would be relatively cheap and simple compared to the tunnel), b) there's a competing (though hopeless) proposition to have it preserved for some sort of railway use (presumably a "heritage line" rather than actual transport). Either way, it gets to stay open!.