Here are some Danish typegodkendelse in PDF form, which are documents used to specify an approved build and construction of a mini. The 1275 GT is particularly interesting as it also shows disc brakes as an option. Feel free to use them.
Below is a copy of a Letter from Rover in Germany allowing a mini to be built to ERA specification (with Turbo and ventilated discs)
Below is a copy of a hand written document from Skat (the danish tax office) that they used to calculate import tax on a 1969 mk2 mini. (thanks to Allan Larsen)
Below is a copy of a hand written note from a DOMI dealer saying it is ok to put disc brakes on a mini.
Below is a document from British Leyland approving that an increase in engine horsepower by 25% does not require any modifications to the vehicle. An increase of 30% requires disc brakes to be fitted to the front wheels.