Ultra Violet Fly and Insect Killer UV Bug Zapper
From Cookipedia
240 Volt Ultra Violet Fly and Insect Killer UK
As our neighbours keep lots of chickens, during the hot summer months we were been plagued with flies, which started to become a real nuisance. This 'kebab-shop' fly killer solved the problem at a stroke.
We found the best place to position it was actually in the conservatory as that was where most of the list was, which seemed to attract them.
It cost £37.59 on Amazon Prime (August 2020):
240 Volt Ultra Violet Fly and Insect Killer - Amazon Prime