theres should be a sticky on this but never could find one
headlights are sealed unit lhd so just swap em out for some cheap ones of ebay something like this:
http://www.ebay.co.uk/itm/H4-HALOGEN-HEADLAMP-HEADLIGHT-12v-conversion-kit-7-RHD-PILOT-/300893286388?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item460ea32ff4" onclick="window.open(this.href);return false;
Your side lights are in the front indicator so if you want you can run the feed up to the sidelight in those headlights, or leave it where it is but not fully road legal
At the back swap your reverse light bulbs for orange ones, pull the indicator feed of each side and attach to the reverse lights (thinks its black/red one side black/green the other).
Then finally as US bus's use the brake lights as indicators, you pull the brake feed wire off the hazard switch (its normally the big yellow in the middle of the group of wires) Connect a wire to this and run it to the back of your bus where the indicator wires were (brake lights), feed over to the other side and that's it your done.
You now have UK legal lights