I would have assumed that you'd get an MOT anyway, after all this work, as an easy way to prove that it's now road-worthy again, (for insurance at least). I think i'd want to get one anyway, like you say, for a 2nd pair of eyes.
I watched a kit-car helper video the other day which said you should get an MOT before taking a car for IVA, which was news to me. I thought that was the whole point of the IVA, but apparently the MOT man actually creates the new entry in the system for it, not the IVA man.
I cant wait to see this thing in the flesh... do you already know which car shows you'll be taking it to next year?