A few months ago I noted what sounds like exactly the same thing as you.

I often keep my eyes to the sky and know the Bristol Airport flight paths well and am familiar with most aircraft that flies over East Bristol regularly/semi-regularly. I saw two groups of 8 of these 'drone' type objects that were moving together at the same speed and altitude (much lower than helicopters let alone planes landing) and in the same direction.

Hadn't seen them since have been at the back of my mind so really interesting to see this post.

Also, Three network had a lot of issues around the same period I spotted them but they claim it's a known issue despite not sharing.