Looks like on one the variegated Euonymus. It is the yellow of the leaves which the flies like. We find that all our yellow flowers are attractive to them.

It's a Euonymus, and I think its Euonymus japonica aureus, rather than Euonymus fortunei Emerald'n Gold. Check the backs of leaves, stems and tops of leaves carefully - lots of flies hanging around might mean you have a Euonymus scale infestation, see link below, you'll need to copy and paste into your browser

https://www.rhs.org.uk/advice/profile?PID=798

If its not that, just make sure nothing's crawled in there and died. Otherwise, trim the bush over to get rid of the flowers - flies rather like them!

I've read that it is one of those plants where flies do the pollination so that's why they like the flowers. It is also said to be used as a winter nesting site for black bean aphids presumably providing food for the flies before the flowers appear.

If those are both true than it's probably not the best choice for right next to the front door.

Thank you for your responses - Bamboo that's exactly what the issue is, looked at the leaves and it's definitely the infection described. Going to get some spray to sort that ASAP - thank you very much.

It's by our front door but it's not our bush or land, it's our neighbours. So the spray will be fine as can be discretely done!

It usually is the cause! As for being discreet, your neighbours should just be grateful you're treating the plant - it can cause a fair amount of decimation over time if left untreated.

Some years ago I grew Euonymus Silver Queen up the bungalow wall and had the same problem with bluebottles. The bigger it grew the more flies we had until I couldn't stand any more. I dug it out and the flies buzzed off somewhere else. Spraying hadn't helped.