Virtually always on FGW services these days, journies beginning/ending in Trowbridge. Most regularly used services would be Paddington to Bristol and vice versa on HSTs. To get to them I usually end up on a 150/158, depending on whether I'm out for The Trans Wilts Express or a stopper. On other occasions, it's 159s on SWT Bristol to Waterloo services. Oh, and of course, occasionally I use the loco-hauled jobs to scoop a winner loco if one produces, commonly between Bristol and Filton.
Do you prefer to travel to London by changing at Bath, than Westbury or direct into Waterloo?
I appreciate that this post is old, and has already been quoted, but I've noticed something. The Trans-Wilts Express? Not to be rude, but last I checked that was the number 49 bus. For everyone besides Techniquest and myself, that is a (usually) double-decker (although annoyingly not when I used it! :-x) -operated route between Trowbridge and Swindon, via Devizes.
I'm going to assume that you mean the former Alphaline route between Cardiff and Portsmouth?
It got that nickname from me ages ago, since a large chunk of the route is in Wiltshire.