I've gone for HID's and fitted these:
http://www.ebay.co.uk/itm/SLIM-HID-C...item33611eb2e1

Mainbeam bulb holder needs a slight mod, but all working okay and a 20W power saving!!

it's pretty simple, but would need new bits to reverse it!
the mainbeam bulb holder is a twist in fitting that the original bulb sits it and the wire connectors are a moulded part of the fitting, so what you have to do is to cut the connector block off of the bulb holder. this creates a hole that the HID bulb and its wiring can fit through. the original wiring has to be cut and 2 spade connectors fitted to power the slimeline ballast.

the dipped beam is more or less a straight swap as it uses the sprung wire fitting, but again i cut the original connector block off and replaced with spade connectors to save space.

the slimline ballasts are stuck under the petrol tank on each side with velcro tape.