Looks as if I have been wrong talking about CCJs. Sorry for being unhelpful and thanks for the correction.
Well you're not that wrong - most small claim court cases do result in CCJs. Every day vast lists of debts go through courts and end up as CCJs.
But let me explain this a bit more since the key factor in those cases is someone with a debt who doesn't respond to letters, nor to the Small Claims process, nor to the judgement. So this is things like Council Tax and HP schemes, where the reality is that Small Claims is just a washing endeavour to get the debt to a debt recovery company and/or bailiffs, since that's when at least a proportion of hard-to-recover debts finally do get paid, and with massive uplifts on the original debt.
If you go to court, you can defend your position and each line of the charge. If the DJ decides on the balance of probabilities (so not beyond reasonable doubt) that nevertheless a debt of £x is outstanding, the court usually gives 14 days to pay (and sometimes take a few days to send that out, so 3 weeks in practice). If you pay that judgement within the time frame, or even a little after, then there is no CCJ. Furthermore the DJ can also accept a case for staged payment plan over time, longer than for criminal cases, and that too avoids a CCJ even though it may stretch for 2 or 3 years.
If someone actually engages in the process, it makes it quite difficult for large entities to manage this cost effectively - legal fees cannot be recovered except to a small amount. There is also a new requirement for mediation in contested cases, which may work well for the OP but large outfits absolutely hate it. So frankly many companies in this position scare their customers but heavy language and random threats in order to dissuade them from engaging, in the hope the big bill will somehow go away. Typically it won't but then the debt recovery agencies are often effective.
On the other hand it seems from post 1 that perhaps only one fare is wrongly charged, maybe a few more, but the OP did have the railcards for the other fares. But we need to have more information from the OP about exactly what happened here and previously. But if it's just that one fare that is missing, presumably a few pounds, then they should pay that in using the bank details provided in the solicitor's letter. If there are other fares that SWR has come up with, well that needs to be proved, but I bet they also missed the railcard letter too, so they just did a data dump of all railcard tickets on SWR and assumed there is no railcard, that amounts to £1600.
Debts can be recovered for 6 years in England, the Magistrates requirement for 6 months hearings on summary cases is not relevant or connected here, but notice how the solicitor carefully worded this to look like a threat but actually was not a threat.
It would not surprise me if the solicitors have agreed to take on this case on a "profit share" basis. If they realise there is only £10 in it, their interest may wane.