I am a bit lost myself what is C&G 3?
The OP probably means C&G 2330 parts one, two and three.
I have c&g 2360 1,2 /2391 insp +test
do i join nic pay them then go on my merry way or does someoe need to inspect my work?
If you do domestic and aren't part P registered, then yes, you either need to join NAPIT or ELECSA, or similar, OR you need to notify building control yourself who will charge you a fortune to "inspect" the work you do.
Absolutely yes, is you are taking on work in your own right. You will need a minimum of public/product liability. Speak to a broker about trades insurance.
do i need to be employed?
Um.....employed in what sense? If you are the employee of another business, then it is their responsibility along with yours to ensure you are correctly trained for the work you are doing. If you are self employed, or have started your own company, it is your responsibility to ensure you are properly trained for the work you take on.
Not sure at all what this question really means.
if i want to sign off my own work do i need a buiseness address with health and safety posters etc or can i use the cupboard under the stairs.
Again, if you are self employed, you can trade out of a cardboard box, if you choose. To a certain extent the same is true of you form your own company - H&S posters are only applicable if you employ staff. If you are a limited company, you need a registered address.
does joining a scheme provider put me in better position to get jib card or do i need a jib card to join a scheme provider?
which is the cheapest scheme provider?
No, joining a scheme doesn't put you in a better position to get a JIB card, - good work, experience, and qualifications do.
Cheapest provider depends on your specific requirements - talk to them.
can i use my girlfreinds house for test and what do they want to see ( do i need to do a full rewire )
You can use ANY work you've done, so long as it meets the requirements - essentially they want to see it is safe, of a quality, done according to the standard, and that you know what you are doing.
Again, talk to the scheme providers and ask them what they will accept for assessment.