I just walk on with confidence, i travel regularly with a bike from london and around the country (mostly to south wales) never book it just act like its what you are supposed to do and i have never had a problem. I do abide by the no peak times rule :)
done a bit, london to bristol on the canal path (after all that rain last year was horrid) but i have enjoyed riding abergavenny to brecon along the cannal then up to builth and back down to monmouth really recomend this.
This thread is inspiring, must make monster!