Look like helicopters. There are at least a few British military installations in and around Herefordshire, including the SAS if I recall correctly. I think the USAF base at RAF Fairford is also only 30-40 miles away.
If you watch the complete video, closer to the end you'll notice the distance between the lead light and the other two is getting greater. That tells me there are not three lights attached to some large, fixed size object.
Yes, helicopters can and do fly in formation. The military would make night time formation flights during exercises. Here's a video that shows 5-6 helicopters flying in formation. You can skip to about 1:45 in the video to go straight to the formation flying.
I tried to find a video of a night helicopter formation, but couldn't find one from the perspective of the doorbell camera. This video, however, shows a single helicopter approaching a hospital at night in light fog that I think looks quite similar to what we see in the doorbell video.