I am not a supporter of the "Secret Squirrel Brigade" and keeping secrets etc from other members, but in this case I think it is warrantied that the dangers far outweight the advantages to your Lex.
The figure I got a few weeks ago wasnt expensive for the time and the knowledge that you are getting, yes maybe the components only cost a couple of quid from Maplins but we all know that anyone can buy a soldering iron from there and claim to be an electronics wiz (just like I did lol!).
I would much rather pay for someone to do it for me and know that I havent wired the red wire instead of the pink wire and and then be on the M6 and kaboom my pride and joy is a pile of ash and melted plastic.
If someone is willing to pay £300 for a rear spoiler to be fitted by a Pro then I am sure they are willing to pay £x (whatever the amount is) to get total closure fitted by a pro. As someone would be willing to pay me (well my company !) £1000 Day for me to setup their Novell or Citrix Servers... I could tell the customer how to do it on the phone but then it opens up a whole can of worms with support etc....
So in conclusion, if you dont know how to do it and it isnt as simple as "bolt this to that etc..." then I think its worth getting a pro to do it, and if there are any problems with it then its their problem and not yours.
Sorry to rattle on guys
Dunk