I did buy cat6 shielded cable to do this work but I came across a problem trying to connect to the shielded modular plugs where the cables are too thick to go through the holes of the plugs. I have tried three different makes of plugs with no success.
Are you not terminating your cables with RJ45 socket faceplates?
If you do go with shielded cable I think best practise is connect shield to ground at one end only to avoid group return loops. This would be the end nearest the main grounding point as in a "star" grounding layout. Also I think regs state that you should run your networking cables in a separate conduit than mains voltage. Hopefully other people can confirm/refute this before you pull cable.
You can reduce interference by crossing mains cables perpendicularly but maybe the option to do that is limited judging by your post. As a side-thought, I wonder how much interference one of those HomePlugs would generate on a parallel-running mains cable.
I can empathize with your RJ45 plug frustration having gone through many different plugs as well but I did eventually find shielded plugs that did accept fatter cat6 so they are out there!
However, we're nearly into 2018 so why not be the envy of your neighbours and do it properly by installing fibre? "Yes, I have FTTP - fibre to my privy" No interference issues plus attaching a short patch cable can double as an emergency laser toy for the cat! [joke and legal disclaimer icons go here]
[Edit: separate conduit note and reducing interference paragraph]
Edited by dohmniq (Fri 13-Oct-17 09:27:56)