I feel you bother have recently been in your shoes.
I got my level 3 2330 when I was 18 but not much else on paper. I had plenty of hands on expearience - but this is just words, again nothing else on paper, so I did all on my own and expence!!.
Competancy: So your got your tech certificate (L3 2330) this declares you compentant in what you do with regards to design, install and generall principles ONLY.
Knowledge: You need to prove you can demonstrate your required knowledge of current 17th edition regs - are you up to date to amendement 3?
Expearience: Then you need to prove you can demonstrate your overall competancy in inspection, testing and commisioning installations by means of a 2394/2395 qualification/cource which is a expearience oriantated examination which is not easy to pass, but well worth getting. I know this because I have just completed mine
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Then get in touch with your preferred scheme, pay then an arm and a leg, then they normally arrange an assessor to meet you on a job you are doing, assess your work as well as your qualifications. Then if all is good, you will pretty much be on your way.
Part P is not really in existence anymore, despite this there are con fast-track cources kicking about which claim to get you qualifications which are not industry reconised so be cautious.
Hope this helps.
Regards
Jamie