I googled it; sure enough, can't find UK police vehicles with one. Perhaps it's a policy decision where clearing a road is left to tow trucks, which would take longer to arrive. Obviously there's separate liability there in allowing the police to do the "pushing". And perhaps, in a country of more compact dimensions, the added 1+ft in vehicle length is considered to be not worth the benefit.

Generally yeah, tow trucks or specialist wreckage recovery vehicles do this here (UK), however, in an emergency, it's not uncommon for fire trucks to ram things out of the way too.

What else are they going to do it with?