X10 Din rail wiring questions

["graham_howe" <graham@xxxxxxx>]

I am finally about to embark on rewiring all of the lights and
switches in the house to make use of two big consumer units housing a
total of 19 din rail modules. The wiring from the modules to the
lights and switches will be as follows:
- T&E from module to light
- T&E from module to switch
- multiple lights on a single module to be connected in parallel
- multiple switches on a single module to be connected in parallel

Questions:
- I may run CAT5 to each switch location too, though I am not sure
what it might be used for at present. Does anyone have any suggestion
as to why this might or might not be a good idea? Note that this wire
will almost certainly have to run next to the T&E for a significant
part of it's length.

- When the wires run back to the consumer units there will be a total
of 38 wires (1 for switching and 1 for lights in each 'zone'). Is
there likely to be a problem if these wires run together in conduit.
I do have a good gap between the din rail modules in the consumer
units.

- Is there any particular specification for the T&E wire. Do I
actually need T&E wire for the switches (I know that some light
fittings require earth so I am putting earth to all lights) as all
switches are the clipsal momentary ones.

Finally the big question:
I want to do one room at a time (with the intention of redecorating
as I go) so ideally I need the new consumer units to be 'live' for
the first room. I do have multiple circuit breakers in the new
consumer units, so I can safely work on individual zones. But I have
never actually connected up an additional consumer unit, so can
anyone tell me how I need to go about this. Idealll I want to start
on the first room this weekend, so if connecting up a new consumer
unit means getting an electrician in then I need to know pretty
quickly. Of course, if there are any electricians on the list who can
get to Milton Keynes this weekend and would like to quote a price for
installing a pair of consumer units then I would be delighted.

Regards

Graham