The much more to this story, at least from the Marines end is force protection. Since the Marine barracks in Beruit was blown up with great loss of life, after mission accomplishment, it is the highest priority mission the Marines recognize. I was in some ****ty places in Africa, South East Asia and elsewhere and we had some particularly primitive accommodations as the better ones were deemed unsafe from a protection standpoint. A bit of a downer to see other services in air conditioned buildings while the Marines are in a tent away from anything with deep trenches around. Just part of being a Marine.
Even if the Brits had overall responsibility, the Marines should have had a security plan in place accounting for such an attack. I can all but guarantee that Marine elsewhere have received guidance to be prepared for this.