upvc french door not shutting properly?

The gasket/seal can be replaced fairly inexpensively but maybe best to get a joiner/glazer to do so to avoid further problems and it sounds like the lower part of the locking mechanism is jammed in either the locked or open position. As this could be caused by a few things, some very simple, again with a decent joiner shouldn't be overly difficult/expensive to fix. If a 'push up' handle to lock, then try looking down at the part that isn't working with door in the open position and maybe you can pin-point the problem. Alternatively, the door may be ill-fitting to begin with. Best of luck

Martyn
February 2010