marky - you dont mention how much the gold trowel course is? or if youre working part time or on benefits? how are you pulling in the cash at the minute?
lets just say you landed a job workin for 2 spreads, they'll keep you movin without you havin to pick up a trowel, youll be worth 40 quid a day, its when its quiet and theres only work for 1 spread that youll get your training cos itll pay them better for one of em to take a day off and the other to take you with em...youll still mix up/clean up/make tea but youll still have loads of time to pick a trowel up and get used to it, you might even be given a cupboard to do all on your own but you'd be better off learnin to flatten off and more importantly WHY!
if you land a job with one spread on his own to be honest, all youre gonna be doin at first is mixin and cleanin etc so until you can at least flatten off good youre not really worth 40 quid just to knock up a couple of buckets of skim, clean a few windows, sweep the floor and make a brew...unless the bloke is particularly generous...he may as well spend an extra hour a day and keep the 40 quid...
SO...what you need to think about is how you can make yourself of some value, maybe offer to work for your lunch and a few beers, it takes some of the sweat out of the plasterers day and he'll be grateful for such a willing worker, stay on the rock and roll for a bit (i didnt say that btw its a bot/virus :

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then, give it a couple of weeks and while your standing around waiting for him to give you sommat to do (assuming youve swept up/cleaned down and kept him in tea) grab a trowel and offer to start flattenin off...after a short while he'll realise your actually savin his back, youll get a routine goin flattenin off behind him and youll be worth 40 a day...
shortly afterwards youll get a chance to have a go at layin on...week later when youve managed to get most of it on the wall instead of you/the floor etc your gettin there...
keep watchin how he does it though...thats how youll answer your own questions mostly...
pick someone older than you, someone your own age would see you as a rival and tend to take the p'ss and keep you on the broom (testosterone innit)...we've all got sommat to prove when we're young! well most of us anyway!
best way to get a start locally is just put the word out your lookin for some plastering training and are willing to provide effort, 2 arms, 2 legs and some common sense in return, maybe the odd meat pie...and when i say put word out i mean tell everyone and anyone, not just who you think might give you a start, cos people talk, tell your gran, the postman, the ugly bint that fancies you down the chippie...anyone...except gordon brown
if you find the right bloke/team youll find that the more you put in, the more youll get out...but above all dont expect it to happen overnight, youll need 6 months experience minimum...then, when youre makin your own background suction decisions etc, and making your own mistakes, thats when you really start learnin