@Brian123
I've ridden all of it between London and Long Buckby. (live in MK) as others have said, the tow path is great in places, shabby in some and in the current weather, rutted and difficult.
unfortunately one of the best reasons for riding the canal (the plentiful pubs) are closed.
i would also say that prepare for punctures unfortunately as the tow paths are lined with Hawthorn.
there are plenty of wild camping spots if that's your thing and for the most part, supplies would be easy to get a hold of by wandering off the canal a few minutes in most towns.
its a ride ive planned for years to do but something or other gets in the way. tbh, id probably get a train to Bham international and ride back from there if i fancied completing the ride.
let me know if you go ahead, i can help with local knowledge in the MK area.
all the best