Good news, Graham. Though I'm not sure I'd describe a service with the last train of the day at 7:30pm from Westbury on weekdays as 'all day' - hopefully a 9-10pm departure could be added over time?
I thought about that before I posted, and decided that "day" means daytime - from around 8 in the morning til 6 at night. It means that people working during the day can use the train, including (now, just) people working in retail in Swindon on a Sunday.
There should be a later train that 18:32 from Westbury on a Saturday ... and later that the 19:35 (ish) the rest of the week. A further cycle of the same unit? Understand another crew would be needed and (commenting here in a slightly private area) we have been quoted what looks like the price of a complete shift for driver and conductor, with a need for two of each to run 7 days. 4 staff at £how-much each, plus operating cost of train and track access charges and you'll see it's an awful lot of money. Need to find something else to do with the crew / train, or have it more sensibly integrated at another timetabling point.