My handset did not reboot for about 24 hours and I was eerily happy -- keeping my fingers crossed that this process had solved the random reboot problem. However, as soon as Google Play installed a few app updates the phone, it has since rebooted around 5-6 times in just a 12 hour period.
and
The phone whilst in complete default state still had the random reboot problems.
Which is it?
The first sounds like when you had nothing installed / updated it was fine. Then you're trying to change your statement.
It can very well be that there's an issue with an app update (Google Play handles all apps and updates). The app update in question could mean there's a problem with the phone's software -- it could also mean there's a problem with the update. It's just, without knowing with app it is, nobody knows who to contact.
If the phone runs fine without an apps or updates installed (your "eerily happy" statement suggests that), then that's most likely the case.