It's excellent that you're working on home automation (particularly in, and for, the UK!) It's going to be a big market. I have some observations on your schematic - I hope you don't mind me commenting...
1. It looks like the voltage developed across R1 is dependent on the power of the lamp in the fitting. This may be ok with incandescent lamps upwards of 60W, but I'm not sure it'll work with low energy, or lower power, lamps.
2. You have a 1MEG resistor (R3) in the gate drive to the triac (T2.) The TICP206 needs the order of 8mA to turn it on - You won't get this with 5V through 1MEG.
3. The leakage current through triacs is quite high, so with low energy lamps you may get flickering, and worst case could damage the lamp fitting (electronic) ballast.
4. Your system allows only switch off - not on - if the mechanical switch is on (as it appears that the terminals are in parallel with the triac.) Of course, you may not be intending to fit a mechanical switch too...
I continue to look for an elegant solution to cheap, electronic, control of low-energy cfl lamps (as an (unhelpful) aside - I absolutely hate them, but we're all being forced to use them, even though the technology is rubbish - LED needs to catch up quick!) So far relays have been the only reliable solution for me.
I agree with your X10 comments - I really don't think much of it at all. The nicest system I've seen is based around Crestron equipment and KNX. It wasn't my system, and it cost ££££££s
I hope these comments are of some small help.