You can do ceramic coatings yourself, only certain paints take it, I think.

I think bmw / mini push the product quite hard but if I was having it I would find an expert dealer. Really though, are you preserving it for the next owner? If you only keep it 5 yrs then just use it. Modern paint is pretty crap out of the factory.

I think the best money spent is the 3m type self healing protection films on the front and high chip areas.