Flies!

Arghhh!

There are so many flies i'm going crazy!
It doesn't matter where in the house I am, theres about 4 big flies!

I've got a fly curtain up at the back door, thats not doing anything! They are attracted to the fly paper i've put up, so i'm chasing them around with household flea spray, which is doing the job!

Can anyone suggest anything else to kill them?
I've cleaned all rooms, so theres deff no food/crumbs etc, and there doesn't seem to be any particular room that has more, so I think they are coming from outside!!

How about a UV plug in killer? No bad chemicals there!
Becky