We use a UV lamp over the door ... attracts quite a few ... also a 'tennis racket' zapper to get the ones inside .... otherwise, keep your bedpod zipped up from early evening on, and they shouldn't get in.
I have always used fly spray...sparingly and not sprayed directly onto the tent material. I have heard all the stories that it ruins waterproofing but I have only heard rumours and no proof. It certainly hasn't harmed any of my tents. I have no doubt if I were to spray it in large amounts directly onto the tent material it may not do it much good but just a quick squirt in the air is enough to kill flies already inside and deter others from joining them for a few hours.
Cheap UV lamps don't seem to work and in any case may attract flies in from outside. Citronella certainly doesn't work...I have seen flies and wasps land on the container for a rest then fly off again. Electronic bats can be fun for an hour or two but flies are usually quicker than me and the effort exerted doesn't show equal results...and the equipment knocked off the tables and smashed has to be replaced.
You never see bugs flying over or around nettles, pick a few hang them up in awning or put them inside a jug; you won't get the nasty devils flying around , cheaper than fly spray.