I've just had a new softwood window fitted (cottage style).

http://www.jeld-wen.co.uk/popup_chos...=12&subtype=14...

After fitting I noticed that the top mortice fastner was tight, so much
so that the brass effect paint had already began to come off. That
said the window did close. Since then, the window has been stained and
left slightly open. Now, the top mortice faster won't close, no matter
how hard we pull we can't seem to pull top part of window in close
enough to fasten, despite the bottom mortice fastner and stay being
in closed position. I am really trying to establish the root cause of
this:

a) mortice fastner may have been fitted slightly out, thus not allowing
for natural expansion and contraction

b) staining in cold/damp conditions has caused window to expand

c) window has warped - fitting?

etc.

Who should I go back to - builder or stockist (Travis Perkins)?

As always, any advice greatly appreciated.