right update.

after i realised the hinge had a large up and down play and finding the screw mechanism completely bent, i began to think the play in the hinge bolt is unsafe and caused the weight to be placed on the latch on the other side, thus bending the screw.
i dunno when this happened, either it was there when i bought it, or was too loose on my 20 mile ride and ive caused it.
either way i dont feel safe on the bike. ive ordered a new latch to see what the play is like with that, but assume the hinge is knackered and will cause the same issue.