Following the advice here I intensified my search and starting with the 0906 a couple of dashcams forums (yes, there is such a thing!) suggested the chipset in the A119S (https://www.amazon.co.uk/gp/product/B01HN0HBFG) is the most up to date there is (at least from the "China" market) - I decided in the end not to have a rear facing camera (I could always change my mind on that at a later date).
So I took the plunge and bought the one listed in the link above - this has the GPS mount, which means you get speed and location (as well as self-adjusting time) stamped on the video too - it also has quite hi-res (1440p HD) setting - although I am operating at a slightly smaller resolution in order to save on file size.
I also bought this (https://www.amazon.co.uk/gp/product/B01N0GR4ON/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1) mini hardwire and Fuse kit to allow me to stealthily install the camera behind the rear view mirror - I really don't like the big bulky cameras and the wedge shape of this unit helps make the fit quite "sleek". I wired it up - to a permanently live spare fuse slot (for now) - and using the movement detection/ parking modest will "wake up" and record when there is movement in front of the camera when parked up - when driving normally it just records on a loop as normal.
Now I know that the wisdom is that there is a risk of discharging the battery by staying permanently "on" - certainly I would unplug it if I left the car for a week or so in an airport car park (or at home under its cover) - I just wanted to see what it was capable of at the moment. (I currently have my battery jump starter in the boot with me in case it does decide to flatten the battery!

) I will probably end up putting a hidden switch somewhere allowing me to switch the camera off when I wish - thus having the best of both worlds.
I've only driven with it a bit, the quality of the video is very good (and that is not at its highest res) - I took photos when installing and will happily post up how I did it if any one was interested .... it only took me 3 weeks from buying the car to pulling bits of trim off the car fitting a "mod" - didn't take me long
In the meantime - here are two pictures of the camera fitted - the lens of the camera is adjustable side to side as well as up and down - this allows me to compensate for the fact that the camera is mounted on the right hand side of the rear view mirror.
Cheers
Christopher