Good point. I thought this didn't apply to off-peak returns, but it seems it does. So I should in theory be fine to disembark 'early' one way and/or embark 'late' the other way, so long as I get an off-peak return, if this is to be believed -
Break of journey
Break of journey is allowed on the outward portion of Off-Peak tickets unless otherwise indicated by a restriction shown against the ticket's validity code and in all cases on the return portion of Off-Peak return tickets.
You may start, break and resume, or end your journey at any intermediate station along the route of travel on Off-Peak tickets unless the ticket restriction for the journey you are making does not allow it. If you intend to start, break and resume, or end your journey at any intermediate station, please call 03457 48 49 50 to check if it is available on your specific journey.
Having said that, now I look here -
http://www.nationalrail.co.uk/ - it seems that single tickets are often quite a bit cheaper than on the site I was using -
https://www.thetrainline.com/
Does anyone know why that would be? Who gets that extra money on those prices, and why does Trainline (which I thought was the NRE site until just now - it has their logo on it) claim to help you find the cheapest tickets for your journey if they are sometimes priced higher than on NRE? And also why NRE only lets you book in advance up to April but Trainline allows you to book up to July?
According to NRE a single from Hull to Newcastle is more than tenner dearer than a single from Hull to Edinburgh, when using the exact same train, from the same platform at the same time, but just staying on for a lot fewer stops?! How can that be right? Confused!