Hi John,
My tubes come from Homebase (10mm aluminium tubes, 10mm external) and I use 8mm FG rods (available from any model shop or online)
So far, never had a fit issue with the Homebase tubes
(they go up to 12mm ext - 10mm int.)
For the elevator, same, Homebase brass tubes and 3mm piano wire.
Pretty much all my stuff is in storage, but I'll have a look for the rods what I have at hand, if I get the time! (still at work at the moment :!: :!: :!: )