Hi Duncan, my preference is for Lagartun or UNI oval tinsel rather than wire, I think wire's too bulky in relation to the amount of flash you get from it. For a 10 I usually go for small/medium and for 12s/14s I go for fine/ex sml.
There's so many places that stock saddles that it's hard to pick one. I usually shop around for the ones I get. Tom Savilles in Nottingham are my first stop for Metz cock or hen, or Celtic Flycraft if Savilles haven't got what I want. After that it's Lakeland for whiting, if they're in stock that is.
Yep, normally hen for the shoulder hackle in my case although some use cock hackles.
Hope that helps.