...but then the OP was using the cheapest junction boxes this side of a
very cheap place...

I rest my case.....

The Wickes ones are about the same price and are far superior quality wise.
I know you can get even better ones if you pay more, but cost isn't really
the point here. The Screwfix ones are BS marked, which leads you to the
conclusion that they might be cheap but *shouldn't* be dangerous. These are
dangerous.

Andy