The
OP▸ is saying he's used 2 tickets Bath-Didcot and Didcot-London but has used services that don't stop at Didcot. This is way it's a bad idea:
When you make the journey, go to Swindon as per the single ticket you've bought. But don't get the bus to Didcot, get the bus to Reading. Then, from Reading, get a train to London. Your Didcot-London return is 'Any Permitted' route, so this diversion is fine, and you miss out the hellish stopping service from Didcot-London.
No, I'm afraid that this diverson is not fine. Unless one (or more) of the tickets is a season or zonal (e.g. rover) ticket and the other is not, your train (or in this case, your bus) must call at the station where you swap from one ticket to the other. If you did try to use a Bath-Didcot ticket and Didcot-London ticket on a nonstop service from Swindon to Reading, neither ticket would be valid for that part of the journey and you would be liable for a Penalty Fare of ^53 (twice the Standard Open Single price.) The only option here would be to get the Didcot bus and put up with the "hellish" train from there.
Then comes the crafty bit. On the return journey, get on the London-Bath service. You know, the one you'd have had to pay ^50 to use. Again, your ticket is 'Any Permitted' route, so effectively you could be changing at Bath.
No, your London-Didcot ticket is not valid for changing at Bath. The only time it would be were if you were traveling out of Waterloo via Woking and Salisbury. And as your service is traveling nonstop from Reading to Bath, as explained above, you would be liable for a Penalty Fare this time of ^87. So again, you have to travel on a service that stops at Didcot.
When I've given the ticket over after leaving Reading, I've feigned confusion and explained that I'd planned on changing at Swindon. Which, of course, isn't one of the stops on the diverted service.
And if anyone asks you before Reading, then you just use a similar story. They can't do anything, because of the status of your ticket.
I've only done this journey a few times, but the last time I did it, the cost was just over ^17. That's for a return journey from Bath-London. Yes, it's a bit complicated, but Christ it's worth it!
So far I would say you've been very lucky you haven't been caught. I would suggest that you either spend just over ^17 and put up with stopping/changing at Didcot, or pay a little bit more to via Salisbury or pay a bit more again and go on a direct train. I wouldn't push my luck as at the end of the day, it may well end up being cheaper to have bought a Saver First Return for ^125 rather than be forced to pay the Penalty Fares!
Hope that's clear. I can ramble on when my tired!
Cheers,
Mike
