I was about to buy a chainguide and 32 single ring to fit my Deore cranks. Before I do, though, if I fit a cheap bb chain device, to see if it suits is there any reason not to use the middle ring from my 3x set up just for now, whilst I see if it all works for me ?

It worked for me. Though I didn’t even bother with a chain device (just the old mech centered over the chainring) and only dropped the chain once in six months.

…..runs off to garage to bin ( ok not that brave yet 🙄 ) front mech !

Thanks !

I’ve run two bikes single chainring for a year and only used cheap, pressed steel shimano chainrings. With a guide never had problems.