UPVc window - broken mechanism

[123batfink]

I've got 2 UPVc windows that won't open. I have removed the handles and tried inserting a screwdriver in the mechanism and turning it that way. This seems to open half off the window but not the other. As though 1 or 2 of the bolts are getting stuck.
I spoke to a repairman, who said it would be a really cheap job to repair if the windows were open. Unfortunately, they're not! Any ideas how I can force them open?
THanks

[Chris]

Try to gemmy the window open from inside using a very wide bladed metal chissel or similar. If this doesn't work then you may have to remove the glass then gemmy agian.