Wow - thanks everyone for you input.
@Boater Sam I had a quick look at the Leeds and Liverpool, looks intriguing. Is there any particular stretch that's better for the rural aspect? And any renters that you could recommend?
@Mike E-W Thanks will have a look.
@NickF @Cheese @Peter X I'll discuss the pros and cons of 1 vs 2 boats with the rest of the party, but I'm guessing they'll agree with @Cheese that 2 will offer more comfort.
@Peter X We're happy to do locks. Think it will be necessary for a bit of exercise after sitting around on board :) Mostly a pretty fit bunch, so that shouldn't be a problem. But I don't think we want to do 8-hour days with locks all the way. Some uninvolved cruising and landscape-gazing time would be nice. And enough moored chilling out time, would be equally important. Thanks for the CRT link, will take a look. Most of the group have done several canal journeys in France. Those of us that haven't have quite a bit of general boating experience, but none of locks, so that guide will really be helpful.
@OldGoat Thanks for the thoughts. As I type, the more I think 2 boats will suit the group better. Although this would be more expensive, we only all get together sporadically, so it's probably worth the outlay to make it a more comfortable and memorable experience. I think we'd prefer the canal system over the Thames, just because it would be novel for all of us.