Brian--- My wife and I have hired narrowboats in the UK more times than we can remember. We also visit good friends in France and have seen (by air and from shore) much of the Canal du Midi.
While the canals in France go past interesting places to visit, the canals themselves are very boring compared to the older, narrower, and "do it yourself" nature of the canals in the UK. The French canals, being newer, are wide, composed of long, straight sections, and are often lined for miles with plane trees. The locks are operated by lock keepers or in some cases are automatic.
In comparison the British canals are winding, passing through a huge variety of environments-- in one instance sneaking beneath the city of Manchester literally through the underpinnings of some of the larger buildings. They climb hills, they cling to the sides of narrow valleys, they cross rivers on stone and iron aqueducts built in the late 1700s-early 1800s, and you run all the locks manually yourself.
France is a great country-- I am half French-- but compared to the canals in the UK, the French canals compared to the British canals are very boring. Not where you can go, but running a boat on the canals themselves.
Interestingly enough, of the people I have met who have done both, almost all have said the same thing.
And the canals in the UK, while muddy, are quite clean. Not so the canals in France although I'm told they are getting a bit better in this respect.
We love traveling in and exploring France, but doing it by canal boat holds no appeal for us having seen the canals.