Start with a good service, covering all aspects of the car including suspension, brakes etc. Maybe even put it through an MOT, it might not need one yet but £40 for a complete checkover of the car is good value. Track down the oil leak and sort that.
Then I would start with handling and braking first, making sure everything is in order and doing the things you want.
Then you can think about engine tweaks and mods if you want
Next would be interior and exterior tweaks.
I also think a fibreglass bonnet would look great.
Wheel wise you are a bit restricted, but there are a few options. Easiest option is to go 11 spoke TF wheels and custom paint them like I did.
[img][img]http://i625.photobucket.com/albums/tt333/CJJ326/MGTF/Projects/Wheel%20refurb/DSC01142.jpg[/img][/img]