I completely agree with the OP with regards to Southend.
I visited last year in a 172. I spoke to one of the security guards upon entering the terminal building to say I had arrived in a private aircraft and just needed to pay a landing fee. I wasn't asked for a passport (which is lucky because I had no ID on me!) but nonetheless had to queue for twenty minutes with a load of EZY passengers and surrender my half-drunk bottle of water even though I had brought it with me in the aircraft!
The "computer says no" jobs-worth approach and surly attitude displayed by the staff means I won't be returning in a hurry. As others have commented I suspect they don't really want any GA visitors at all, so perhaps this is their intended outcome.
Such a sad contrast with their ATC who are always a pleasure to deal with - a real pity they are so badly let down by their ground colleagues.