Ah ha! 
View menu screen shows correct PM2 reading now and an AQI level, the main screen graph now shows the AQI and it is being plotted (see attached). I will need to investigate how AQI is being calculated so can’t vouch for that but will assume correct as PM2.5 is correct.
The AQI charts are being updated in the webfiles folder but don’t seem to change their timestamp, properties shows to have been modified rather than rewritten so I assume that is normal?
I’m off to bed now but will check again first thing, it certainly looks ok 
Thanks Brian
Cheers
Nick
