As mentioned above, the Tuesday Night Club covered it all (as far as England/Wales are concerned, not sure about Scotland) then effecively disbanded to explore Ireland and places further afield. Their website is excellent. Maybe Neil Arlidge will come on here and give some more details.
In our case we've been to very nearly everywhere that we can reach in the connected system, counting since we first got our own boat in 1987. That DOES include such stretches as the Bristol Channel from Gloucester to Bristol, most of the Middle Levels and the Great Ouse tributaries, the Witham Navigable Drains and Kyme Eau.
We have NOT yet explored the Basingstoke Canal (always been stopped when we've been near), the Wednesbury Oak Loop (BCN), the Titford Canal (BCN), the L&L from Wigan to Liverpool, Bow Back Waters, the River Ouse etc (Yorkshire), the Sheffield Canal (we're too long now), the Calder and Hebble Canal (we're too long now), the Rufford Branch (we're too long now), or the Lancaster Canal (we're too long now). There's not much on that list that we can still reach, and we're hoping that maybe we can get to the Basy next year and perhaps add Droitwich to the list too.