Draught through ill-fitting windows

[rolyatescort]

Our upvc lounge windows have terrible draughts. The draught comes through the two opening sections of the windows. If you cast an eye down the length of the opening section you can see it quite visibly bow as if it is being wedged into a too small aperture. Is it simply poorly adjusted during fitment? I assume the windows aren't actually bending due to not fitting the hole?

 

[Gazman16]

Pics?
A slight bow may not be a problem it depends on how bad really.
You say the draft is from the openers? Try to work out where from. Usually it is from the hinge side which means the hinges are wearing/worn out.
Give the hinges a good clean and lubricate them. Especially get some Vaseline in the triangular corners tabs.

 

[rolyatescort]

I've just taken some photos so will get them on to photobucket shortly.

The opening panels are approx 4ft high by 1.5ft wide. They lock at the bottom and open upwards.

The bulge is at the centre point of the height. It is sufficient to get the tip of my little finger in on both panels. It appears to be slightly below the resting point of the hinge