So after a LOT of forum searching it does appear they should be illuminated and the culprit is likely to be a connector loose in the back of the sound system.
This makes sense as the previous owner fitted an AUX USB interface, and it's a bad one! I'm now dithering about a Grom vs Xcarlink but when i do fit one of these I'll check all the plugs are seated properly, and get my upper display re-soldered.!
Check the seatbelts, there is a label sewn on the bottom that gives date of production. Petrol cars spark plug leads if original usually have a date on them as well.