Since it's fitness rather than dislike of locks, that opens up a lot of flights which normally have volockies in summer or where they can be booked. This is definitely a good thing if you're looking to cruise for a month or more at a time
Lower Peak Forest has the most spectacular local scenery as you're going through a steep valley without any locks (it does have windlass-operated swing bridges though) and you also get access to the Macclesfield. If you want to explore further in your month away, you can pre-book volockies to do the hard work of taking you down through Manchester to the long lock free Bridgewater/T&M sections you know (Marple normally has volockies anyway, CRT will take advance bookings for the Ashton & Rochdale Nine)
Leicester Line of the GU has miles of rural lock free cruising, plus the volockie-operated Foxton and Watford flights which are as easygoing as boating gets. If you're happy to do 6 relatively low-rise and well maintained locks down to Braunston sharing with another boat for assistance, that opens up much of the North Oxford, and via Hillmorton (4 relatively easygoing locks that often have volunteers) you get the massive level section that includes the Ashby
The South Yorkshire locks are electric (and fill gently too) and the cruise range is absolutely huge if you're prepared to do the tidal Trent (lockkeeper-operated locks and a lot of electrically operated lift bridges) as you can also get to Lincoln (no manual locks) and Nottingham (one manually operated lock). You do have to be confident in deep locks for large parts of it though, even though you shouldn't need to use ladders.
With much of it being rivers rather than canals, you go a bit faster and have fewer places to stop, and I think the other two routes are prettier, especially for short trips out.