| Ended up buying off the ebay guy (£155) who really couldn't have been more helpful. Fitted it last night with no problems, all I needed was a soldering iron and some shrinkwrap. Scary as hell to start with but actually a doddle once you start connecting the wires up.
Can't recommend the guy enough, he knew all the best places to cut into the loom on an SL, took my panic calls at 9.30pm, and told me to keep his number in case anything goes pear-shaped later.
He has about 15 System 3s left in stock:
Mike Burnside
07973 335525 or
01256 703593
Cheers,
Ali | 
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