I expect this has been answered in part before but I can't find it all
in a search, so perhaps I can tap the expertise here for my issues.

My phone line comes into the house in the hallway (a sort of extension
on the front of the house) and has previously been bodged to split
there and send one line to a (BT but not NTE5) master in the kitchen
(via half a mile of cable through the garage) and a secondary socket
upstairs. I'm in the process of changing broadband service and I
thought I might sort all this out as part of the change. (Although
I'll check the new service works OK before changing anything) The
general opinion seems to be that the broadband filter should be as
close to where the service comes in as possible, for the best signal.
The idea is:

A) Put the master socket where the cable arrives in the house. (Yes,
I know I'm not supposed to touch BT's side but they won't know if I
don't screw it up, and it will regularise everything. In any case, a
while ago a tame BT man who came to fix a fault gave me some cable and
jelly crimps to sort the wiring out, so he doesn't mind at least.)

B) Split/filter the cable at the master and take separate feeds to
the phone and router.

C) Take two runs of cat5e cable from the router to my son's room, so
he can plug his computer and Xbox into it and stop moaning about games
dropping. The wireless box should do for more trivial applications,
like me and the missus working from home (!).

Now the questions:
When I split the service, should I take the runs to the router and
phone in telephone cable or cat5e? It doesn't matter on cost grounds
as I have plenty of each, but which would work better? Is it even
worth worrying about: As the data path to the house is pretty mucky,
in old cable from whenever it was laid, will the little bit in the
house make any real difference?
If I use cat5e, I presume I can take the filtered and unfiltered down
the same cable, but how do I make up a reasonably good looking cable
for this? (ie prettier than just the strands going to plugs). I've
thought of heatshink to cover the strands but this may not be ideal -
Would 2 short patches (of phone cable) into a double socket, then
cat5e behind that, laid in trunking to the outlets be better?
Has anyone used the decorative trunking (D-line from Screwfix for
example) and found it to be good or bad? (I was wondering if it would
ever open again once closed!)

Any thoughts/experiences gratefully received.
Cheers
G