The point of entry is in the top loft - a dormer bungalow remember - and the room is very limited with no flooring etc. As I said before the lead then goes down behind the upstairs sloping plasterboard walls into the lower attic space again with no flooring & a long crawl & again very limited space - dropping to skirting board level before coming through the plasterboard into the upstairs room where the master socket is located.
Given all that I am looking at solutions.
Which picks up interference worse? :-
1 the incoming wire before the modem
2 the cable between the modem & the router
3 the cabling between the router and the final wall plate
I am guessing that the modem should be as near to the entry point into the property as possible but I don't know how important that is nor the relative importance of the above
Interference ... i depends on where the source is relative to the cable. It also depends on the cable type. Flat untwisted will pick up interference easily, twisted will cause it to be rejected (without going into too much detail).
Of the three you have, only the incoming wire to the router will be susceptible to noise. Once it has left the modem it is Ethernet which runs at a much higher level and the noise level is right down so unlikely to cause any problems.
My personal preference and recommendation is to get the modem on the line as early as possible. If you can do that and then in your own time feed some Cat5e along the route of that cable you can then put your router where you want it.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
M H C
taurus excreta cerebrum vincit