Not surprised the Devizes line isn't well known, for much of the 20th century (until closure) it really was just a typical little GWR branchline which, apart from Devizes, didn't serve any significant population centres.
There were through trains running on to Newbury, Reading and Paddington although in the latter days these were very infrequent and poorly timed. The line has no real 'claims to fame' apart from one on-train shooting in 1889 (the headmistress of a Devizes school being the victim) and a visit by the Flying Scotsman in 1963.
A large variety of trains have run on the line over the years including railmotors, flying bannanas, and various small tank engines providing 'local' passenger haulage before giving way to first generation DMU's. On the loco side, Halls, Manors and Castles were regulars on the line. In later years, Hymeks and Warships made regular appearances.
One of the last trains to use the branch, on 2/6/1965 (6 weeks after official closure) was D1010 Western Campaigner on a royal train. This stabled overnight on the branch with the Queen and DoE on their way to Castle Cary. After reaching the stabling point (near Holt Junction), D1010 was detached and ran light the entire branch to Patney whilst D1041 was attached ready for onward movement of the royal train in the morning.
The signalboxes were especially reopened for this to happen.
Regarding the route I am producing, Westbury - Holt Junction is still very much open, with the line running on to Chippenham and Swindon seeing more trains now than for many years (until December when there will be some significant cuts). HST's also regularly operate over this section (on diversions).
After Holt Junction, the now closed Devizes line went almost completely straight and flat past the outskirts of Melksham then near to several small villages (Seend, Sells Green, Bromham and Rowde) before climbing up over a mile at 1 in 60 to reach Devizes. Just after Devizes station is Devizes tunnel, 190 yards long with a castellated portal. This tunnel is now home to a shooting range (where Michael Ryan of Hungerford infamy 'trained'). After leaving Devizes, there is another small halt which used to serve the local assylum. After this, it is a pleasant run through countryside before reaching Patney and Chirton where the Devizes line rejoins the current GW Paddington - Newbury - Taunton line.
In the route I am constructing, Westbury - Holt will be 'as is' but the branch itself, although featuring realistic scenery and local buildings, will reflect modern practice and be somewhat rationalised with some of the smaller stations being closed.
There is still some way to go constructing this route - I cannot give a likely release date as recent improvements to my coding skills ensures some sections will be rebuilt. Apart from the trackwork at Westbury and the Shredded Wheat factory near Holt, there are not really any 'difficult' objects to build, so when I restart (after a small extension to the Clarendon route), progress should be reasonably swift with the possibility of extending further along the GW mainline if desired.