Cheers guys!
It is a total doddle to do. Just remove the trim inside the boot (2 x 10mm bolts then loads of friction clips), unbolt and remove the wiper, unbolt the motor (3 x 10mm) and disconnect, tape up the cable to tidy, clean up the hole, grommet in with a bit of silicone. Took me 10 minutes and cost less than a fiver, and you can always just pop it back on if you feel like an undo.
Evo-R diffuser:
http://www.evo-r.net...diff/index.html
Bit of a pig to fit as you can't easily clamp it while the silicone dries, unless of course you remove the whole rear bumper, so I ended up bracing it with a plank and a trolly jack for 24 hours while it cured. Did the trick!
Really pleased with the carbon bits on the black car. You can't really tell from a distance at all, so it's all quite stealthy.