Two Tunnels is an enjoyable trip, been a couple of times. Last time I decided to complete the circuit and return to Bath along the K&A Canal, having decided to RAIN I wondered by the time I got to Bath if I would have been any wetter cycling down the canal, rather than the tow path.
I have cycled down the canal, when it was drained many years ago (1980s?) to be repaired. A wonderful experience.
For anyone who is going to do the round trip including the K&A towpath, which I would thoroughly recommend, note that the towpath does get very busy with pedestrians, particularly at weekends, not to mention anglers, boat users and others.