OK SQX, many thanks - That works … Sort of…
I’m getting a temperature reading, but it’s nothing like accurate - I wasn’t expecting 3 decimal places and would have been happy with +/- 1 or 2 degrees C. But i’ve placed the sensor (carefully) in ice and I get a reading of 11 degrees 
- just a bit high!
However, at room temperature, it seems to be OK (ish). Looks to me like there is a bit of non-linearity going on here. I also don’t understand the 45/1024 bit of the code - I assume that is some “fiddle factor”. 
This has been a good learning experience, but I think I’ll be looking towards the LM35, as there seems to be better reports on this device.
Thanks again SQX, much appreciated.
Ken.