Insect and Spider Identification: Cant find a match for this spider would love some help, 1 by CattUk

CattUk wrote:
Hello,
I live in the Uk, the spider lives under our alarm box, there is a constant red flashing light and rarely pops out. Was able to get some snaps whilst it munched on a bug before it raised its front legs and crawled back under. I'm having great difficulty in finding a satasfactory match.

Its front is jet black, a slight green shimmer on its fangs, slight hair on the legs, the abdomen is a silky grey with a blue/grey line from front to back. also a raised bumpy outline around the outside of the abdomen kinda like a pasty.

Thank you for your time,
Catt