When i looked into this deciding what to do, it seemed to me that the 2392 was for single phase stuff like what you see in a house and is the sort of level for a DIYer who wants to do his own thing and not worry if the council comes in to check.
2391 covered three phases and is more at the level I would expect to see of a wet behind the ears electrician who could walk into any installation and have a clue about what was going on. So entry level practical, to be backed up with several years experience learning the job before one could call oneself an 'electrician'
And for the original poster, where you need to start depends on what you know already. if you have got O'level physics (or whatever they hand out nowadays, probably an A level before you cover simple electrics) you pretty much covered all the theory. So don't accept people telling you it's going to be too hard to start half way up, they need to ask questions first.
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