As I need to rewire my new house I thought I'd take the opportunity to add
some home automation ... however there are so many options and all the good
ones (star network with DIN based switching) seem too expensive for me just
now. So how difficult is it to convert from ring to star?

Would it be possible to:
-Run the ring to sockets and switches in conduit through plaster initially
If / when budget, time etc allow use of c-bus or similar
For a socket
-draw-out ring cable from conduit leading to socket
-use a junction box in under floor cavity to make ring continuous
-drop star-cable into socket
For a light
- using existing ceiling rose / junction box in under floor cavity to
continue light ring
- connect light fitting to star-wired DIN-Dimmer
- draw-out live/switched live cable to switch from conduit
- drop in c-bus control cable to switch box

I understand that in the recent regulations junction boxes are frowned on,
but they must be used for lighting circuits and if running a garage circuit
from a consumer unit (or are you expected to run SWA cable through the house
too). So if these are acceptable is the above use of junction boxes OK???

TIA
Jon