I've noticed that the steel reinforcing tube that runs to the side of the windscreen panel has become detached.

Any suggestions on the correct adhesive to use to stick steel to fibreglass.

Appears it was a kind of silicon material previously, there is no place to use mechanical fixings unfortunately.

Sikalfex, tigerseal or similar PU adhesive will do the trick.

I've used araldite also.

Araldite would be a little brittle in my eyes. I think a silicon or PVC would work better.

When I was a kid I used to fix my nitro suspension towers that were carbon in a similar way. I used little steel rods that were silicon sealed in place. They used to work a treat and take a beating. I found that the araldite would crack after one 7 roll tumble!!!

silkaflex can be painted over silicone cant both will give goos adhesion