Jaslan and Svennilenni - thanks very much for your help, which has led me to a solution!!!
I tried all your suggestions and they didn’t solve it, but got me thinking that if all these relatively niche things were correct, it had to be something basic. Looking at some guides to recording for beginners (and I’d looked at a lot already!) one described how to set up the folder in which files would be saved and their related audio kept also. I had had it set to ‘use default location’ so I clicked the ‘prompt for project location’ radio button instead (on the main cubase opening screen) and set up a new folder as the default storage. Then I created a new project and immediately saved it in the same folder and noticed a folder named ‘audio’ had also been created in that folder. I set up the track as I had been doing before, recorded some guitar and, hey presto, I could finally play it back as well. Looking back at the previous set-up, there was a new folder created each time I started a new project, but that only contained an empty folder named ‘audio’ and nothing else. I’m not sure if it was the folder structure set-up that was wrong, more likely I just needed to save the project in the correct folder before it would associate it with the audio?
Interestingly, I could still not see any waveforms on the recorded track until I used the vertical zoom, at which point it became visible.
Anyway, I am very grateful - it’s been a while playing around, but seems sorted now. Many thanks again.