Thanks for all the comments.
Cat5e faceplate - Yup, that might be an idea, M-B. If I can find some conduit to tidily mate with it cross-section wise, this could be a solution!
90 degree bend - no problem at all if the conduit has such large cross section as to make the cables so loose they are rattling around. Falling off to sleep last night though I wondered about using a large section flexible hose like the one I have with my Aquavac - and which I am not about to cannibalise!
Load bearing walls - I avoided this detail since it was irrelevant to the conduit question, but here goes: The vast majority of the conduit run will be in free space behind plasterboard in the cavity left after removing a coal effect fire. Okay, not strictly free space as it will need to lightly squash the thick "loft" insulation that is now there, but the point remains the same; all but 3" (vertically) is not even brick, let alone load bearing, and the 3" I will need to chase out is not firebrick either (in case anyone wishes to resurrect the fire when I am dead and gone). The plasterboard is not fitted yet, so the job is easily done.
WiFi - No thank you, not even N. I borrowed such a router and found loading photos from my NAS was not as snap-snap-snappy as it is with my current Cat5e setup; Not slow like G, but still just slow enough to be irritating. In any case this doesn't solve the problem of having 8 other signal cables to hide and connect that are unrelated to home network connectivity.
Niche companies - Precisely. I just need to find some - hence the thread
Cheers,
TLXV