Just a word of warning regarding First Class availability on services in and around the Bristol / Bath Spa / Westbury area. With regards to the improvement works at Bath Spa and the mass changes to the timetable; It appears there has become an assumption that Class 15x Trains have miraculously grown First Class seating...
For some reason several trains are showing as having First Class Accommodation and also appear in the Online Journey Planners as having such accommodation too. Yet when the train turns up you actually get a unit of Class 15x type. Which of course does not have First Class seating.
The way would check is to put the time of the train into realtimetrains.co.uk and then select more detail as shown here:
This will bring up the below information. You are looking for the "Pathed as:" information. As shown below, this train is advertised as having First and Standard Class seating. But the "Pathed as:" information shows as running as a Class 150/153/155/156 Unit - which of course will not have the First Class seating.
If you find yourself on one of these phantom First Class seating trains; I would advise contacting
FGW▸ and raising a compensation request under condition 38 of the National Rail Conditions of Carriage:
38. Travelling in standard class accommodation with a first class ticket
If you have a first class ticket (or the equivalent) and the first class accommodation (or the equivalent) shown in the National Rail Timetable is not available in any train you travel in, you may claim a refund of the difference in price between the first class and the standard class ticket for the relevant part of your journey.
As said earlier in the post, these trains
ARE in the National Rail Timetable as having First Class seating.
http://www.nationalrail.co.uk/times_fares/46427.aspx