I'm picking this is an Evo or something along those lines (I hate the term but, a boy racer car), and you want it cause it's cheap. If so, it's been THRASHED, it's cheap because it's nearly dead.
Re-reg, probably crashed.
5 month WOF might be nothing, or it might be green/pink sticker.
Plates changing is probably related to personalised plates.
Security interest applied when the dealer sold it to someone who used finance.
The car is dodgy. Just walk away, this is a lesson you don't need to learn the hard way.