[Smudger]

totally agree with rg1 - any 'cutting' compound will not polish uPVC - it will brighten and clean but destroys the ultra smooth extruded finish ( basically melted plastic forced through a die )
the solvent will replicate this as it 'melts' the upvc restoring a smooth surface - we are talking about light reflection and for the most part light use of cutting compounds would not look that different from the original finish

Darran

[Kenny83]

As posted earlier... i think silicone spray is whet your lookin for...  after you clean, hand apply to the frames, it gives a prtective barrier aswell as a shine