Brits have a technique of using SAS/SBS under cover to take down bad guys by surprise... They have used it against the Provos for years. I suspect they were doing the same against traitorous police (recall that we have seen articles about police "hit squads" in Basra) and something went wrong. They then had to get the "lads" out and used force to do so... Its a dirty war and things don't always work as planned.
My father was party to some SAS activities way back in the 60's, but not a million miles away from Iraq. They would spend weeks in a town or city, and blend in with the population, speak the language and look the part. These two are wearing trousers and t-shirts, not exactly what the locals tend to wear. I don't think they are SAS, at least if they are not on a long term operation.