Hi Nigel,
i used a low level switch on the reservoir...
Brake fluid level switch by
marlinpeter, on Flickr
Pedal switch....
Foot brake switch by
marlinpeter, on Flickr
and the BMW handbrake switch which confirms the lamp works...
Handbrake "On" switch by
marlinpeter, on Flickr
If I did this again, i'd build a little cover over the switch as I tend to bend it with my left hand when i get in and out of the car.
Not sure if the IVA has cahnged things but i think not,
Peter