I'll keep it quick... The cover of my battery cavity has broken & I need a new one, but have no idea where to get them from!

It's one that has a hinge & you push it down at one side, & clip it out to change battery.
It's the hinge part that's broken, so at the minute it's just clipped in.

Anyone got a site for the UK that sells them?
Or any advice for me?

electrical tape is your friend.
if you really want one, any electrical store will sell the whole thing but probably not just the cover.