In any case, the website is probably not set up to allow refunds for an 'Advance' fare type at the passenger's say so, as a refund is outside the T&C...
But not in the case of cancellation of the service the passenger was booked on. A full refund is still applicable under the National Rail Conditions of Carriage.
E. YOUR REFUND RIGHTS
26. Refunds on tickets that have not been used.
If you decide not to use a ticket (other than a Season Ticket - see Condition 36) to make all or part of your intended journey, then:
(a) if the train you intended to use is cancelled, delayed or your reservation will not be honoured, you decide not to travel and at that time you return the unused ticket to any ticket office, the Train Company responsible for that ticket office will, wherever possible, give you an immediate full refund
I do think however that the staff at Bodmin could have completed the necessary paperwork and forwarded the ticket to the retailer for the issuance of a refund under the
NRCoC▸ . NRCoC says a refund should be issued, wherever possible, at any ticket office. That
'wherever possible' though is a handy get out clause for ticket offices to refuse to issue refunds when another retailer is involved. But they should still take in the ticket and complete the necessary paperwork to forward to the original retailer if their own systems and/or local policies prevent them issuing an immediate refund.
You could try again at a staffed station but it may be more productive to contact the original retailer.
FGW▸ support for online sales can be called on 0844 556 5605*. If you are reluctant to call this non-inclusive, revenue sharing number then you may be able to be put through to the web support team by dialling 01752 675640.
Alternatively you can email
fgw@custhelp.com*Which incidentally has no details of the cost of the call on the FGW website, which goes against Ofcom guidlines.