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...

If the tube inner and outer are carbon fibre then this will mostly take all or any loads, the inner clear part may not need any fibre reinforcing at all?

Why not set up two carbon tubes with the clearance you want, stand vertical , blank the bottom and fill from the top end with a clear casting resin?