I use autoglym HD wax, by far the best/easiest to to use for the money imo. If you check reviews on it it'll say it's hard to beat. And 2 coats every 5-6 months will do it.
I think private reg plates are great, had mine for 12 years. What I would say though is get it personal to you and not the car because you'll have a different car one day and then it's just wasted.