Does anyone know a company that could make me small quantities of a double walled tube? The first (inner) tube to be 1.5-2mm wall, clear resin with a single layer of 80gsm woven glass fibre (preferably as close to the inside of tube as possible), the outer tube to be “normal” carbon fibre with standard 1.5mm wall and the outer diameter to be 25mm.

Odd request I know...but then I did say I was the mad scientist...

There is another problem with your idea. Glass and carbon got greatly different young's modulus. Wich means that your resin layer will take huge loads under stress, because the outer layer will deform less than the inner one. And every matrix failure will make it less translucent. Worse: the cut offs on the outer tube will cause stress concentration on the already weakest parts of the tube. Additionaly you will get high shrinkage stress due to the unfilled casting between two solid tubes.
If you are really planning a  structural part, you should take a grp tube, that can take more than the calculated loads, as the carbon tube will be more of an additional load, than an reinforcement.