Stripped screws - problem locking door

[Gem83]

Hi, We have a problem with the screws on the external door between our kitchen and the lean-to.
The screw holes seem to have been stripped and the screws keep coming out of the holes causing problems locking the door.
Any ideas how we can fix it?
It is a glass and PVC door and the lock bit is metal, we have tried bigger screws but they don't fit.
Any suggestions? We don't really want to spend £700+ on a new door

 

[foxhole]

Screw holes? where? lock? hinges?

 

[Gem83]

It is the screws in the side of the door which attach the piece of metal that holds the lock in place.
Does that help (sorry, not very good at technical stuff)