redfoxa23 - Just to confirm that the symptoms on my HDR1000s are identical including in Windows only being able to see the HDD in device manager. In Linux Mint in Files I could see all the recordings but do not seem to have an app to play them. I also noted that if I connect the HDD via the USB on the front of the 1000s it identified the storage but no files. It gave me the option to format and as I do want to try and recover any recordings I chose the option and it worked.
The HDD I have is a Seagate ST3500322CS P/N 9GW132-510 and top right on the label is Video 3.5 HDD. The "new" HDD is same ST but P/N9GWW132-012 and top right on the label is Pipeline HD.2. I believe having trawled Google that the "new" HDD was actually replaced by the model in my 1000S. It would be nice to know if either of these HDD's would work in my Foxsat HDR?
Re the Arris - I would be reluctant to buy the HDR version until it has been reviewed more. I am no expert in this field as you have probably realised! However I suspect many of the problem issues currently reported would relate to functionality of no use to me. I live in the very NW of Spain, no land line, and rely on mobile phones and 4G wireless router for internet - all metered. As an end user providing it efficiently identifies the channels I currently have it would pass muster. Having my 1000s repaired by sending it back to UK would not be cost effective. I could of course buy a reconditioned 1100s for £270+ or even a new one for £599 form Amazon UK! The bottom line seems to be if you want a new Freesat HDR you only have one option.