These officers were probably SAS or on loan from the SAS.
Counter-terrorist police officers in the UK are taught CQB either by the SAS or by people who were taught by the SAS.
So it's possible these were cops, from anti-terrorist squad or special branch, or maybe security service spooks. It's possible that they were SAS but my guess is that they were cops. There are only a couple of hundred badged troopers in the real SAS, and they're mostly kind of busy elsewhere.
Dumping the guy on the ground hard, sitting on him and putting a clip up his nose is 100% pure SAS style though.