I'm probably telling granny how to suck eggs here, but here goes.

I'd noticed that my back window doesn't always go back up when I shut the door.
Slam it, something I don't like doing, and it works.
I was going to post on here for advice but took a look and I noticed that the lock was a bit loose in the door.
All I did was tighten the two large headed Tork fixing screws.
The window now works first time every time, even with the door being gently closed. Result
May be something for others to bear in mind and check first if they have trouble.

Thanks will do that later on dads as I always feel when I slam it I'm gonna have a boot full of shattered glass!