Hi
I have used this for builders cleans and is like using T- cut, its good if you have a small area to clean but if you have a lot of upvc to clean then its going to take to long, so i would recommend the other 2 upvc products that screw fix sell, i use these on builders cleans all the time and highly recommend them.
The solvent based one cleans anything off with ease mind you DO NOT put it on coloured upvc it will take the color off (i now from experience
)
They also do a detergent based one which is excellent for getting upvc clean.
Hope this helps
John