Thank you for the replies Tony & Mark.

Tony, it looks as if they brought in a feature to disable the idle timer from DSM3.2-1922 onwards so I will have to upgrade (no big deal) - thanks for the heads-up!

Mark, I will be using the Synology NAS OS to do the formatting/partitioning so hopefully, being a recent version of Linux, it should be 4K 'aware' - is this likely? Can I check this (eg. via the terminal)?
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Peter.

"I spent 90% of my money on women, drink and fast cars. The rest I wasted." - George Best