Thanks IanL-S you were spot on - I had to roll back the firmware to Jul 3 firmware to solve the problem, I got a few posts on the Toppy forum which helped me last night

The unit is still chugging excessively at times, everything stops responding for approx 30 seconds and then 75% of the time it will reboot. Which is really annoying as I've only seen it doing it during recordings, so obviously the recordings stop when it reboots.
I'm pretty sure the HDD must be on it's way out

It wasn't a cheap PVR, $669.00 from IceTV directly online, and it's only about 16 months old. I'm guessing warranty won't cover the HDD? What do I need to do to get it replaced, just fit a regular 3.5" HDD myself or is it more involved.
I'll try that TAP "HDInfo" thanks IanL-S, I've remained ignorant to TAPs and haven't bothered learning about them!