I believe you've faced a similar problem before, the trout. Sorry to hear you have faced another cock-up.
In the first instance, you need to complain to
FGW▸ as it was their employee who failed to sell you the product you asked for. I've checked and there is a ticket as you described. Which I'm sure you know!
Future reference: Ask the clerk to enter ZONE U123* LONDN (or 0791) as the destination and to select the Anytime Day 1st Single, Route: WARMSTER-SALSBRY. Whilst it's handy to know this precise information it shouldn't be behoven of the passenger to provide it.
Include those destination details in your complaint to FGW as well. You should be refunded for any additional expense above the ^43.85 you should've paid and if it were me I'd be asking for that refund by cheque not Rail Travel Vouchers. FGW may try and wriggle out by saying that the subsequent tickets sold in error are not their fault, but it was their clerk's failure in the first place that led to those errors.
Hopefully FGW will refund without too much hassle, but if not then you should inform them you will be escalating the complaint to Passenger Focus pointing out that the failure to sell you the correct ticket is a breach of the rules for impartial retailing - something that is part of their franchise agreement.
It's disappointing that the FGW clerk initially only offered you a ZONE U123* if you went via Paddington. A FGW route where they set the fare and take the lion's share of revenue. Probably not deliberate, but it's the sort of thing which Passenger Focus and the Office of Railway Regulation are there for to prevent.
ATOC» 's guidelines to rail retail staff are quite clear on the issue of impartial retailing:
ATOC Retail Standards Guide
C.1 Impartiality
This is the most important requirement and is necessary because Retailers will be selling tickets or giving information about different TOCs▸ .
Retailers at impartial Points of Sale must therefore act fairly and impartially between TOCs and any information that is provided must be factual, accurate and impartial (TSA▸ clause 6-30(1)(a)).
Impartiality simply means providing the customer with information or a ticket that is the most suitable for their needs. Retailers must not favour their own train services, or those of any TOC over others in providing information or selling the ticket.
Where a customer asks to purchase a specific fare for a specific journey, this can be sold without giving any further information (TSA clause 6-30(2)(d)).
In many cases only one fare will meet the customer^s requirements as only one TOC provides a service for the journey concerned. Even where more than one TOC is involved the customer may be specific by stating their requirements in terms of:
^ Destination station
^ Ticket Type
^ Train
^ Class
In these circumstances, the Retailer only needs to seek further information when the customer wants to make a journey that cannot be made with that fare. An example is a customer requesting a discounted fare at a time of day when this fare is not valid.
Where the customer does not specify which fare they want and more than one is available that may meet their requirements, the Retailer must seek additional information to enable the correct fare to be sold. If more than one fare is suitable for their needs, the Retailer must explain the main features of the alternatives impartially (TSA clause 6-30(2)).
Note: TSA = Ticket and Settlement Agreement. An agreement signed by all TOCs which sets out clear obligations for them on the standards they are required to meet with regard to the selling of rail tickets impartially and correctly.
