That particular module requires phase and neutral so it has to be wired between the mains feed and the light fitting, rather than simply replacing the switch. I was thinking about gettting a couple for my living room lights.
HE do actually make a switch conversion module which is designed to be fitted behind an exisiting switch (
http://www.diy.com/diy/jsp/bq/nav.js...&isSearch=true ), however it is dimmable so won't work with non-dimmable light fittings, or standard energy efficient fluorescent lamps etc. It connects to the switch wires and it has a couple of flyleads to connect to the existing switches terminals. I guess it might be possible to use that without a switch, I would think that it would need to be fitting in a pattress box with a blanking plate hidden in the ceiling void, with the flyleads terminated in a connection block and insulated. (I should warn you I'm not an electrician - just in case you hadn't already guessed

)
The remote I have, which came with the set of 3 switched socket adaptors has 5 pairs of buttons and a slider to change the codes of 4 of them. Each device can be programmed to respond to one or more pairs of on/off button, so it can independantly work 5 devices easily, and up to a maximum of 17 using the slider. They do have some much nicer remote controls at a price.
I haven't really looked at the dimmer modules other than when trying out the in-store display when they came out

so I couldn't say if they cause any noise, the sockets just make a click when they switch so I assume use a relay, I use them with a PC and cctv camera and haven't noticed any electrical noise.
You can find the instructions on the home easy website
Home Easy - SAVE your environment!!! they also have a forum so you should hopefully be able to get better answers to your questions.