My Swindon to Cirencester route KUID:30024:100068 is a "re-imagineering" re-work of part of the old M&SWJ, taking the current day Swindon and Cricklade railway and extending it slightly at either end.
I'm sure someone somewhere must have done the line along the Devon Coast and/or down to Torbay and Dartmouth. (If not, I'll add it on my potential "to do") list. Not sure if anyone's done Ashburton or Kingsbridge yet.
I'm fairly certain there's a version of the Fairford branch to the DLS - probably the "ultimate" GWR branch line.