In response to many questions, here's a map showing railways in Wiltshire and also across to Bath and Bristol.

You can see FOUR main lines running East to West ...

London via Swindon to South Wales (in Orange)
London vis Swindon to Bristol (In Blue)
London via Westbury to Taunton and the South West (Orange)
London via Salisbury to Exeter (orange)

The Cardiff to Portsmouth service, with a branch off to Weymouth, is shown in green running from South East to North West.

The (as truncated from December) transWilts line is shown in Brown ... you'll notice it's the ONLY service from the North East corner of our map to allow journeys directly to the South - it connects Swindon which is the largest town in Wiltshire via Chippenham to Melksham (pop 24,000 and growing), Trowbridge (the county town) and Westbury. Until December, this service CONTINUES to Warminster, Salisbury (the only city in Wiltshire and a major tourist spot) and Southampton.

You'll note also some major projected frieght flows shown in yellow.  Some are running already, but additional flows are being added with grants and licenses ... basically from the South West, from Southampton, from quarries in Somerset up to Swindon and beyond for Didcot and the Midlands and North.

Most lines shown are double track.  Exceptions on main lines are West from Salisbury towards Exeter, from Swindon up towards Gloucester, and from Trowbridge to Chippenham.  All three are causes for concern as traffic levels on the railway grow from their low point in the latter half of the last century.  Of especial concern on this site is the Trowbridge to Chippenham section which is scheduled for major growth over a long single section.