We have concentrated so long and hard at working with First Great Western ... but seeing them hiring in units to work the line from other companies makes me wonder "perhaps these other companies would like to / should run the service themselves ..."

I don't think that Arriva Trains Wales are well placed ... their contract is with the Welsh assembly, and their units are based in Cardiff; it lacks logic for them to add an isolated English line to their network.

But South West Trains (who already provide the unit for the 07:02 Westbury - Swindon) are a different matter.  Their trains are actually based on the TransWilts, their crews already know the route as far as Trowbridge, and my understanding of ORCATS is that it could be financially attractive to them, in just the same way that ORCATS makes it financially attractive for FGW to run their 'extras' to Southampton and to Brighton.

It would also bring a sprinkling of competition into the area.  Look at Barry Doe's network map and you'll see the railway centres of York, Derby, Crewe, Doncaster and Crewe showing up multicoloured with a multitude of operators at each.   Swindon, though, is monochrome - just FGW.  Perhaps this monopoly is why train travel to and from Swindon is so expensive ... but that's a story for elsewhere