In article ,
sofadog writes:
thanks everyone for suggestions. I have tried bleach, jif, cillit
bang, nothing works. I think I may give gloss paint a go, but
Homebase have told me there is a UPVC paint, however they no longer
stock it. So, I'm on the hunt for UPVC paint...........

Another thought - there is a PVC cleaner which window fitters
use to clean off any dirty marks they make. It will be available
from PVC stockists (usually found on a local industrial estate).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]