Just to give some closure here.

Last night I finally got around to mounting/using my ER32 collect chuck on my mini lathe.

I flipped the workpiece around since taking that photo above (it's 20mm diameter where I've turned it down...which just fits into my largest ER32 collect nicely).

Anyway, my larger centre drill arrived yesterday so I used that & then followed up with an 8mm drill......it's turned out just fine for my needs.

So it was all much ado about nothing rally ...no drilling undersize & then borring needed. (I still need to revisit why the boring tool seems woeful at erhm....boring - for another day though!)

Coming back to why the drill bits wandered - bit of a mystery ...I'd have to think it was something to do with the tailstock not being fully secures &/or centred (I made doubly sure the tailstock nut was tightened extremely well this time...possibly moved during the drilling process last attempt?) & then using the larger centre drill seems to have helped.

And wow...what a difference using an ER32 collet chuck is on my lathe - it's made the whole experience quick & accurate & enjoyable. I no longer have to think "B0ll0****...there's a turning job I need to do, but that *&$*ing 4 jaw....euugh"