I just thought I would post an update on here about this humidity/temp sensor.
@markus has released a series of drivers that include a "present/not present" capability.
These drivers will also try to get the device back on line should it drop off of your zigbee network.
As I wanted to try and use this capability on this device, Markus advised me to try his "Zigbee - Sonoff Temperature & Humidity Sensor".
I had a few issues initially but that was probably due to me playing with different drivers trying to get the presence to work.
When I changed to this driver, then did a re-pair of the device it worked and has been working faultlessly for the last 24 hrs.
I just thought I would post this info in case anyone else wants to try Markus's driver and get the facilities that his drivers provide.
Thanks.
EDIT: I was using the "Konke temp" driver mentioned in this post and this too was working faultlessly with no issues. Me being just wanted that little bit more.