Might just add that prior to having the enclosure we had a large wooden pergola out back, with black and green grape vines that were harbouring the wasps, where flies come from who knows,
You can get yellow crystals from various ferretarias that once diluted with water will kill flies with abandon.
Anyways we got shut of the vines, got shut of the pergola and the wasp problem all bar dissapeared, we still had some that migrated to a nearby tree but not that many, thats coming down soon so as much as its possible to do we have done or are doing.
The UK has rain and wind and generally crappy weather, we have some flies and wasps lol, we'd much rather be here lol.