Shop broke my item and replaced with secondhand...

[Tired2015]

My camera got jammed so I took it back to the shop, where they told me it happens all the time and they have an expert who can sort it out no problem.

The called me the day after, to say they'd accidentally broken the lens, which has never happened before, but that they have a replacement.

I have tried to use the replacement and find it's not working completely correctly.

I have absolutely no idea, where do I stand with my rights?

The shop has to pay you either to have the original camera repaired or for the cost or a replacement. They don't have to give you enough to pay for a new camera, only what the camera would have been worth if they had repaired it properly. You do not have to accept a replacement from them.