The bikes

Nick rode a steel Dawes Galaxy tourer with triple chainset.  It weighed a ton, probably even before he put his panniers on.  He used his granny gears a lot. I rode a carbon-framed Cannondale Synapse with a Tailfin carbon rack and panniers.  It weighed about 16kg all up, with the loaded panniers. I fitted 28mm tyres and a wide-range 11-36 cassette at the rear, it had a compact 50/34 at the front.  This meant I rarely need to leave the big chain ring, only changing to the smaller ring on the steeper inclines when my legs were tired.  I also fitted a Redshift Shockstop suspension stem to help absorb vibration through the bars on uneven surfaces.  I recommend it.

Both bikes performed well (well, they survived to the end) but mine was not so well suited to the route we took (the Royston Woods route), which included some muddy, stoney, bumpy, uneven, gritty and otherwise unpleasant cycle and canal towpaths - most were fine but there were definitely times when sections weren't a lot of fun.  I was really happy with the all changes I made to my bike, which I am sure helped make the experience more tolerable on some of the surfaces we rode on.  Mud did tend to build up between the frame and wheels because of lack of clearance - a gravel or hybrid bike would definitely be better for that route.

We had only two mechanical issues on the whole trip: Nick started the journey with a slightly buckled rear wheel which became worse after hitting a pothole.  Eventually he had it checked (by which time we were well into Scotland) and three broken spokes were discovered.  Perhaps if he'd had it trued before leaving this might have helped avoid the problem, but of course there's no certainty of this.  I would recommend starting with a good set of sturdy and true wheels though :-)  For me, the internal bracket on one of my lightweight panniers broke but there were no problems with the bike. No punctures for either of us, despite the surfaces we sometimes rode on.