Re the speeding thing, there was a story in the papers recently saying half (?) the Guards don't have the proper certs/courses to turn on their blue lights and chase criminals etc. Apparently they have to earn some experience first by sitting in the passenger seat before they can apply for the course. You couldn't make it up...
And I think the ambulance drivers drive on their own personal driving licence. They've been looking for years to get the law changed because it leaves them in a very tricky situation legally if they cause an accident.
In reality though, if a cop did stop you and there was a pregnant women with her legs akimbo in the back, you'd get an escort to the hospital. But those fecking speed vans would just take your photo and send you a ticket in the post!