That does seen pretty young. Regardless of that, as others have pointed out, you may be called upon to prove your competency. Passing 2382, 2391, Part P and BS7671 17th would be evidence. You may also be called upon to prove how you have kept yourself up to date, joining a P scheme and The IET would be evidence of that. Just watching someone else do it doesn't prove you are competent. If you are putting your name to it, you need to be 100% sure. Just for arguments sake, would you be happy in a 747 if the pilot had learned to fly by watching a mate do it and never passed a test? Ignorance is no defence in law, so make sure you aren't ignorant is my advice.