I would run a Mk2 with around 3.5 degrees of neg front castor, but this is dependant on the wheel and tyre that you are running, something with a square shoulder for example: an Avon ACB10 would need to be stood up and little more at a round 1.5degrees.
Brakes wise I would definately suggest a harder pad, something like a Mintex1144 or even an 1155 if you really use them for trackdays. Disk wise, well you get what you pay for, personally I have never found a problem with running standard (ie non drilled disks) and trackday pads providing they are clear of the rim and if needs be are ducted.
Removing the interior is a good idea for trackdays as it puts less stress on the car (by reducing the weight), You'd certainly want to remove any sub boxes etc from the boot.
If you were running coilovers then it becomes slightly more complex as it begins to involve corner weights, but for the moment you are clear of that.
