Yes you can says my upvc window fitter, but I don't want to risk it!
You can buy special clip on blinds just for upvc windows - am looking into at the moment for my own. I suppose easier if venetian type of blind but I want roller blinds which apparently you can get. Not much info. on the internet unfortunately.
Daizy
May 2009
If your roller blinds will fit to the window or the wall then you are ok.
cyril
October 2008
Yes just use a normal HSS bit slightly smaller than the screw.
Dont go too far