It isn't a long delay, a second or two as others have suggested; certainly nothing out of the ordinary . I probably just need to get used to using it a bit more. I'll have a look at the camera install guide, although I can't see myself making any hard modifications to wiring. Cheers.
I have reversing cameras on my 2017 Toyota Auris and my 2014 Civic 1.6 tourer and the little delay in coming on is no different in either car, I would say it's just getting used to it instead of any issue.