Hi Leo,
It was remarkably easy in the end. Its just the sensors that have caused me a bit of pain, and i think i've worked out why. I believe they are more intelligent than they used to be and instead of a simple open circuit / short circuit, they now have a variable resistance, depending on how much of the sensor is worn out. As I changed mine before the resistance changed ( due to changing because of brake dust rather than wear ), I think the computer doesnt know they have changed ( same resistance ), and thus wont let me reset the computer ( if it is this the software writer needs to add another use case as that crazy ).
Anyway your question.
1) You can either take it to a dealer ( i like working on my car - so didnt want to do this )
2) By an EBrake tool ( about £90 )
3) Remove the eBrake - This is what i did:
a) With the hadbrake not on, chocked appropriatley, open bonnet and remove top of brake fluid reservoir, then Jack up and Remove wheel
b) Unplug the EBrake wiring connector
c) Use a T30 Torx to remove the two bolts holding on the eBrake to the caliper
d) Gently wiggle and pull out the EBrake towards the car, away from the caliper - its got a rubber oRing ( I assume to stop water ingress )- that just sits in a grove so needs a wiggle.
e) Use a 7mm allen key to wind back the ebrake manually. ITs should be VERY easy to wind do not force it. I think its clockwise, but your notice, one was youll only be able to turn it a couple of turns max, and the other ( the way you want ) will turn alot. Once you hit resistance, stop.
f) Remove the two 13mm bolts holding on the caliper - using 15mm spanners to stop the lock bolt spinning
g) Pull the caliper forward ( I used a G Clamp ) to allow enough piston compression to remove the existing pads.
h) Remove caliper and compress piston all of the way - making sure your brake fluid doesn't overflow
i) Insert new pads and sensor. ( The sensor is behind the wheel arch lining on your right and weaves around a bit - 2 8mm screws under the sill need removing to get to it )
j) Now reverse procedure - remembering to tighten the ebrake back to roughly where it was e.g. turn until it gets tight, then go back one turn.
k) Once it the wheels back on turn on ignition and test ebrake works as expected.
Hope that helps
Gareth
( FYi - Fronts are the same as the E85 - But the sensor now connects under the bonnet - which is MUCH better than the rear sensor)
). The service menu is refusing to reset the rear pads. I was just changing to cut down on brake dust. I've rechecked the connection and il looks good, nice click where it engages, but it won't reset to more than 6000 miles ( front is 19,000 I think). I've been for a 5+ mile drive, there are no warnings at startup, ebrake etc are fine, but I want to rest the service trip. 
