Ok, to put some other posters minds' at ease, I don't have issues with buoyancy or trim. Staying in one place in the column and going backwards or forwards with micro control is already within my grasp. With or without mask and reg and with or without doing additional tasks. I'm not moving much. A foot if I'm really screwing up but inches mostly. OOG drills would make nearly zero difference to my buoyancy. I'm not being complacent, I practise it every week, and I'm sure I can get better, much better, and that is my constant objective.
But that's not my primary concern in this thread. If it was I my thread title would have been - 'What do I need to do to prepare for Cavern class' rather than 'Line Skills'
But I do appreciate what people are saying. And indeed I agreed. It's just not probably the thing I'm most deficient in (there's a large selection in this range

)
I won't lose control of my buoyancy trying to deal with a snagged line or having created a bird's nest - I just want to get some advance ideas on how I can prevent myself from making these mistakes in advance. But there's no point in not getting stressed about a situation you can't fix. At some point not being able to fix it will create stress, no matter how good your buoyancy and trim.
I've already gotten some great tips and pointers on this thread, blackwood's videos in particular and the great pointers towards different reels.
I'll get myself one of the cheaper reels to practise tying off and fumble around with different lanyards hanging off me to see just how much I can screw myself so I can work out best way to avoid these. I'll start this off at home and take it to the sea once I've had a longer thought about whether cave diving is something that I definitely want to engage with.
I'm at that funny point where I want more, but not sure what I want but don't think I'll know til I taste it. Whatever that might be. Coming from a rock climbing background I think caves may well be my thing. Maybe, maybe.
Thanks,
John