Grynch, rail travel from anywhere in ‘coastal’ Dorset/Hampshire and Devon/Cornwall is a complicated and stress inducing affair involving zigzagging, multiple connections, and/or possibly several days 😉 And the on-line rail/timetable planners are plagued with logistical errors engendering no faith in the likelyhood of completing of your journey without a some kind of a connection fcukup. One delayed provincial branch-line train and it all goes boobs up!
We’ve have to get our teenage boy from Devon to relatives in the Christchurch area several times a year and we just drive him there now for the sake of simplicity. It’s also several hours quicker.
National Express might be a possibility between major towns. Otherwise I’d drive it.