Draft coming through windows - how to adjust ?

Hi,

I've had my double glazed windows in for about 4 years now. The guys who fitted them cam out last year and the previous year to adjust them.
I don't know what they did to the windows but they tightened them on closing. This reduced noise and draft. Anyway now it's getting cold an night and windy, i've noticed the draft more and the windows are sort of streamy at teh bottom.

My question is on how to adjust the handle or latch etc to make this a nice tight fir whwn closed. One of the downstairs Windows has a gap around 10mil around the top so it's letting in a lot od cold air.

Thanks for any advise.

the "keeps" on the fixed frame that engage with the the rollers and bolts on the opening sash frame sometimes have screws that can be loosened to slide the keep a few mm.

ok thanks i will have a look at what screws are on show