Tom Joyce — nice!
Yes, from what I remember those parts of the journey were still unpaved making it a few bumpy miles for a number of stretches.
The bikes (and tyres) we used were pretty unspectacular. Mine was from Decathalon about 10 years ago I think…
In general though it was brilliant. The chance to see how the country connected together, see some great nature and stop at canalside pubs was an excellent way to spend a few days.
If you end up going for it — best of luck!