Any question answered...

They were all low enough that I could read "police" on the side. I cannot come up with any reasoning for more than one helicopter to be in one area, even if they were in plentiful supply.

The teenager getting nicked could have been a coincidence so feel free to disregard that. But for what reason would four police helicopters be flying in formation? circling a small area?

There is a police training centre in the area, http://www.west-midlands.police.uk/maps/index.asp?map=TallyHo

Mittwoch Aus Licht by Stockhausen - the World Premier!!!!! It includes a camel shitting out glass balls, and a string quartet flying around in individual helicopters. I watched it online last night. Was really good. Honest.