Thought I'd return to the thread to add that, partly inspired by this thread, I have added Brighton to Southampton to my list although didn't have time to go out of my way to connect from the full length of Cambridge to Brighton at Brighton.
I will soon have completed Swansea to Shrewsbury via HoW (the Trainsplit-suggested easier connection from Paddington was at Llanelli but I forced a change at Swansea).
I've also booked the full length of Waterloo to Weymouth connecting to Weymouth to Gloucester as a diversion en route to Birmingham.
And I don't know when, how or why, but I've also resolved to do the once daily TfW 158s from Birmingham International to Manchester Piccadilly via Shrewsbury, Wrexham, Chester and Warrington!
East Croydon to Watford and Gatwick to Reading remain on the list for a future unnecessary routing diversion.