Im not sure what you mean by sliding pva windows?
PVC?
If they were vertical sliders the locks are fairly simple.
If yo mean tilt and turn windows they can be very complicated and you will most likely have to get someone in to look at them. But sash jammers could be used as a temporary way to secure.
Or do you mean sliding patio doors? In which case we may be able to talk you through a repair if you post some pics. A temporary way to secure could be done with these
http://www.euro-secure.com/PatioDoorLock.asp?gclid=CPTpwL_l98QCFQjKtAodFigAiA[/QUOTE]
Hi again Gazman - the item on the euro-secure.com site would probably work. I see it says "euro"-secure! - I am actually in France so might be able to find something like that here. I have also used something like that also on a door where key was lost (in UK). Thanks again!