Easy to do - any good alarm installers should be able to handle this -
My worry would be overuse of the motors in the mirrors - you could be asking for trouble - and I'd say it would be a pain if they constantly retracted even on a short stop at the petrol station etc.
If you want to do it yourself - then theres two options:-
1: Heres an article from FTO UK website.
Equipment required: - Multimeter meter (or 12v bulb) - 2 small 12v relays - nothing special single pole / single throw will do - A soldering iron (+ solder) - Small knife - Insulation tape - Small gauge multi strand wire - eg car speaker wire - Patience 1) Determine where the central locking control unit is in the driver side footwell by un / locking the door a bit. 2) Using a Multimeter (or a 12v bulb) track down the two wires that trigger the central locking, measure where the plug goes in. These are at +12v until the pulse is send to the central locking when it drops to 0v. 3) On each of these wires scrape a small amount of the wire bare and solder on a length of insulated wire, cover join with insulation tape. 4) Gently slider the mirror switch panel out and turn around. Disconnect the big connector. Remove a small plastic cover from above the connector to expose a test connector. Solder two wires to the 2 left most pins, poke in the hole and retrieve at the footwell end (one is mirror open and one is mirror close). Replace panel. 5) Wire up both relays with the following: 1 side of actuator coil: +12v permanent Other side of coil to length of insulated wire 1 side of relay contacts to +12 perm Other side of contacts to length of insulated wire. 6) Connect the loose coil wire to the output from the remote locking unit (for both relays - one for each output). 7) Operate the central locking to make sure the new relays operate with the central locking.
Connect the loose wire from the relay to one of the wires from the mirror panel, repeat for other relay and panel wire. 9) Test by locking / unlocking central locking - you may have open close the wrong way round - just swap the wires. Ensure all bar wires are covered with insulation tape and the relays are fixed out of the way. It is good practice to disconnect the car battery when doing such work but I was worried about loosing the ECU settings (and it keeps you on your toes!). The problem that means all this has to be done is that the central locking produces a -12V pulse and the mirrors require a +12 pulse.
OR
2: Pete Schofield-
ftomirrorkit@blueyonder.co.uk - has designed an inexpensive kit which you can buy. The kit uses two blocking diodes to simplify the installation and requires just two connections at the switch and two at the door lock relay. The kit is only £7.50 and comes with "idiot proof " instructions. Make a cheque for this sum payable to "P. Schofield" and send with return address to:
Pete Schofield,
224 Sheffield Road,
Barnsley,
S70 4PG
and he will send a kit by return post.
(Taken from mivec.co.uk)