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...

What about an inner tube of thin fibreglass, then cast the clear resin section of the tube around the fibreglass tube, then bond that into the carbon tube?

Not an easy process at all for sure. That thin fibreglass is the tricky bit. If you can actually get it made at all, I'm not entirely sure it would work the way you want it to...