In case it helps anyone else
I have just reached out to GWR and asked them to confirm my details were taken correctly and I am still not on their system (incident took place 1.5 months ago)
They have said there are massive delays at the moment, meaning it can take up to 1 year for details to be added and apologise for the delay
thanks - well if they let it go over 6 months from when you were stopped they are only likely to pursue you in court for the civil debt for the unpaid fare owed, as opposed to a criminal prosecution for fare evasion - so the matter becomes far less serious for you if it goes over the 6 month period (ie no criminal records associated with civil debts - at worst a CCJ I believe).
Given what they have said I think you just should keep your notes and copies of all the paperwork and keep them long terms (they can pursue a civil debt for up to 6 years I believe) and don't do anything until you hear from them - which could be ages from what they say, but might not be.
We do see them pursuing cases from 2 years or so ago as civil debt cases so it could happen.
If / when you hear from them - even if it is ages off - head back here for advice - keep a note of your thread title and link so you can find it - as I think after a while inactive threads get locked but mods will re-open them on request if you need to re-activate a locked thread.
There are threads on here involving GWR and civil court action if you wanted to read one - but probably only worth studying carefully after the 6 month and no contact from them situation actually happens