Thanks for the feedback. I've since learnt that apart from the P9, the belt size was standard through the rest of the Rega range.
As for the turntable itself, I've had this bit of kit for years, but having been collecting dust in the spare room, I've decided to restore her and give it a spin in place of my current Pro-Ject 2. Once the new belt arrives, I just need to add a cartridge and then I can see how good it really is. As far as I can tell, it even has the original 'Acos Rega' tonearm with an ADC headshell...
Whilst on the subject of cartridges, any suggestions for a sub-£100 one that will suit this deck. The OM10 on my Pro-Ject seems a decent enough cartridge, so perhaps that would be a good place to start here?
Cheers
Pete