At least LAX CAT is protected up to 10,000. What about carriers flying out of neighbouring Long Beach, John Wayne and Burbank which I believe are all Class C which tops out a lot lower than LAX's . That's a long climb thru Echo to Alpha unprotected (other than the transponder requirement) . I don't believe you have a similar set up in the UK as CAT traffic leaving the protection of a terminal area to climb for alpha will do so in an airway which means any other traffic will be under positive control. I could be wrong and encourage correction if I am