Hello Tim.
I'm using this too at the moment, having just done some internal rigging in the cockpit of a 1/48 Taube and I'm very happy with the results. For the rigging wire I'm using the Modelkasten product which I think has a 0.13mm diameter. I chose the tubing from the large range available from the link hiddeous1973 gave you and an internal diameter just large enough to accommodate one pass of the rigging (i.e no return pass). Unhelpfully from my point of view, the details on the packaging are in imperial rather than metric units.
It reads Transluscent Amber Minature Polymide Tubing, 29 AWG (?), 0.0113" ID, 0.0158" OD, 0.00225" Wall, 30" Length.
One remarkable thing was the packaging. Bearing in mind that it was just a single 30" strand I have never seen anything remotely as comprehensively packaged as this.
Best wishes
Nigel