I've got an up and over door with the lock in the central handle and want to
improve the security.

Due to the gap between the metal edge and the side wood work it is not
really possible to fit any extra bolts at the bottom. I was thinking of
some kind of locking bar/post type arrangement in front of the door but have
only seen one in B&Q and it seemed a bit expensive.

Does anyone know, please, when I might find a suitable product or can off
any advice ?

Thanks
Dave