I’d have thought, in preparation for your trip, you’d need to include some experience for your group of cycling on normal roads with some traffic, and even roundabouts, rather than trying to avoid them by relying on tow paths or cycle tracks. When I used to go on regular local CTC Sunday runs, there was quite a skill/etiquette to riding in a group, with more experienced riders ‘protecting’ the less and looking out for stragglers, and not impeding other traffic too much. In many ways, using an out of town dual carriageway was much easier than convoluted back roads. The ‘old’ A40 towards Oxford or the ‘old’ A4 come to mind. As for your trial run, I’d agree with others that the Colne/Crane/Grand Union valleys would be worth aiming for, such as Harefield or Denham, with several waterside pubs to choose from and many ways of getting there.
Peter Evans ● 95d