Opening a stuck uPVC double glazed window

[NiceCupOfTea]

Ever since we moved in, one of our windows hasn't opened. Oldish uPVC windows, maybe 15-20 years. The key works in the lock and the handle moves, but the window won't budge. It doesn't seem stuck more at the top or the bottom, and I have put a fair amount of weight behind it, but I am worried about damaging the frame or the wall!

Any advice? I was thinking about a rubber mallet but I don't have one - perhaps a few taps with a hammer/wooden mallet on a block of wood?

[NiceCupOfTea]

Thanks guys.

Had a look at an opening window and it just has one sliding bolt in the middle of the window next to the handle.

Taking off the handle it was clear why it wasn't working - the 4 sided bar was missing! Pinched one from another window and it became obvious why it had been removed - the star shaped sockety bit in the window that operates the sliding bolt was shattered and in about 4 pieces (although in place).

It's clearly cheap & old double glazing!

So, would a double glazing co be able to fix it by removing a pane or something? The mechanism doesn't seem to be accessible from anywhere...

[NiceCupOfTea]

What, the pane including that frame, or the entire window unit?

Sorry, that's not very clear - the main bit of the window is not opening, with a top opening and a lower portion opening at one end - it is the lower window that doesn't work. Would we need to replace the whole lot or just the lower window?

[NiceCupOfTea]

Definitely single point locking, but can't see back of mechanism through the glass so can't see what taking the pane out would acheive

[NiceCupOfTea]

Cheers stormin, will have a look when it's light