With all due respect, it is a lot of hassle to go through the process of intentionally using the platform 13/14 barriers and reclaiming the cost when the alternative is just to go through the platform 9-12 barriers and get charged correctly...
Passengers should not be required to deliberately go to the gateline of the wrong platform and then walk towards the correct platform, nor should passengers be expected to know they should be doing this!
Passengers who simply behave reasonably and in a manner that would not be unexpected of a passenger should put in a refund request and I will be happy to assist anyone in this position; the more people I can assist, the better as this could be used as evidence of wrongdoing on the part of GTR.
If you are happy for GTR to get away with it that is your prerogative.
Would it be quicker to just jump the gun to escalate to London Travelwatch / London Assembly Members once TfL refused the refund as I fear that GTR won't be providing positive response either given to current DfT funding climate?
No; passengers need to give the TOC a chance to rectify the matter before escalating to London Travelwatch. However if we can evidence that a lot of people are being charged, we can certainly ask LTW to investigate the matter and contact GTR for comment.
Are passengers travelling on Gatwick Express to Horley regarded by GTR as 'fare dodgers'. There is no concept of fare dodging on Contactless as you are charged for displacement.
Someone who travels, for instance, Victoria to East Croydon to Norwood Junction isn't fare dodging if they use Oyster / Contactless despite going via Zone 5 to get from Zone 1 to Zone 4.
GTR's view of a fare dodger is very different to the reality; they may well view people who either hold perfectly valid tickets, or who use PAYG in a completely correct manner, to be "dodging" the fare which GTR erroneously deems appropriate for the journey.
But that does not make it so.
Indeed I would take anything GTR says with a hefty pinch of salt.