I did it in September - written up in a previous post - see below. I grew up in Compton, my Mum still lives there, so I took the canal route on a recent visit.
It was around 3pm when I got on the towpath, it was a glorious day, so the path was dry most of the way, though could be slippy under foot/tyre in the wet. I imagine it could be a bit tricky if you came across the wrong types along the way, with no real escape route! Even though it was end of school time didn't encounter many shcool kids hanging which surprised me.
Some of the small bridges were steep and unevenly paved as the path under some of the lower bridges, so in the dark would need to be taken carfully, good lights a must I'd have thought.
You could give it a go and see if any other cyclsits do it regularly, strength in numbers kind of thing?
....within a mile or so from Moore Street Station I was on the canal towpath (Birmingham Navigation Main Line). I rode to Wolverhampton where I joined the Staffordshire & Worcester Canal for the 3 miles or so to my Mums house.
Although being bought up in the area I’d not done the canal all the way before. My Marathon 25’s coped well, despite some pretty rough patches and dodgy surfaces, lots of cobbled/brick sections. Coseley tunnel was an experience, nearly 400m in near darkness. Despite the gloriously sunny day I passed very few Black Country folk on the way. Cutting through the urban mayhem, just a few steps away, the 17 odd miles of near deserted waterway, much of it relatively quiet and is an untapped haven, full of wildlife, I spotted several herons and even a kingfisher darting around.
Highly recommended if you get the chance