Hey, your mini is looking great! It looks a really nice standard example, there aren't many of them left! Those wheels look good, a nice set of RSP alloys, and they suit the car
Chrome arch covers look awful

If you wan't to spray your current arches it involves a fair bit of sanding to get them smooth, then prime and paint. I've just done a set in BRG for my car but I'm not convinced to move away from the black yet, I'm a fan of the standard look! It's only £20 for a set of standard arches from Minispares if you wanted to pick up another set and have a go. If you stick with black, a bottle of good trim detailer can get them looking as new again and the contrast to the bodywork can add to the cars look.
As for the dint in the bumper, I have one almost the same from when I hit a wing mirror that fell of the car in front! You could knock it back out, but being such a smooth, shiny surface you won't get it looking perfect again. For the cost of a new SS bumper, I'd just go down that route. There's no great difference in the look between ss and chrome brightwork, and if you get some dinitrol or something in the back of your SS bumpers they should last forever without too much work.