From my experience, candidates with college certificates count for nothing in the real world and have cost me hundreds of thousands in their lack of experience. I'll take a "site trained" tradesman any day over a "college taught" one. I don't care what exams they managed to pass, I'm only interested in what skills they actually have whilst still ensuring they have sufficient certificates to permit them to work.
Remember that the 17th is not a LEGAL requirement, and neither is C&G2382. There is still no such thing as a legal requirement to become an electrician. BUT, when you conduct (excuse the pun) work in a domestic dwelling, this work either needs to be checked, inspected and approved by Building Regs or signed off by yourself, if so approved to do so under Part P.
Therefore, sections that are not covered by Part P (additions, replacement fittings, most things outside bathrooms and kitchens etc) can be done by anyone and signed off on a minor works form by anyone - yep, shocking as it sounds. However, who would use such a person for their job?
Therefore you have two choices:
1/ Go to college, get a whole long list of credentials and finally register and get approved under Part P using NIC, ECA etc and then start as a fully legal and trained "qualified" domestic electrician.
OR
2/ Gain lots of site experience, get your 17th Edition (C&G2382) as this is a requirement for the next step, and then register and get inspected to gain the needed Part P status. You can still attend college when ever you wish to add credentials to your portfolio if you wish.
What is best? I have no idea, but in my opinion it depends on the individual, his experience and skills more than whatever exams he passed sat in a room somewhere.