Submission by Robert de Kloe – Always wanted that expensive feeling of push button lights on/off switching/dimming, here's how I did it : first of all it required some fishing down of 2 extra wires (1 would do it as well but I wanted to adhere to some color coding standards) from the (existing) light bulb to the switch controlling it. If you can't get this done, check out the X10 micromodules – which are more expensive (and they don't have dimmers yet)!
Since here in Belgium Blue=N, Red=L and Black is the live feed from the switch to the bulb I opted for a Red & White wire to add as extra. Once in place I pulled back the bulb end in the attic and connected them appropriately to an LD11 (with some extension wire so the LD11's are neatly mounted in an appropriate enclosure) Black wire goes to switch on/Red wire bundled with white to Live feed/ Blue to Neutral.
From the LD11 I ran a new cable (Black and Blue) all the way back to the original hole in the ceiling and reconnected the bulb. On the switch side I replaced this one with a push on contact internally (and kept the original face plate and cover) in order to score a maximum WAF. The Red live feed linked to the Red wire I put in, the Black and White to the momentary switch and presto. (Blue was already connected – watch out for bathrooms where both circuits need to be switched – you'll need an extra relay to do 2P switching !!).
Now to be completely honest this took me at least about 1 full day to accomplish but as I said – it's an invisible retrofit. (it all added up to about 65 Euro per switch point – cables/LD11/switch/housing).