These days SEN seems not to be problem Jamie-Southend with its only one weekly scheduled flight
All the time we (two Norwegian aviation enthusiasts) stayed at the airport we didn't see any Police, and we were free to take all the pictures needed. Our mission for visiting the airport was to fly with the weekly flybe flight to Jersey. But then we experienced a different first of during our stay at Southend - we were both singled out for a full checked-in luggage check. They emphasized that it was a random selection, but we were the only two picked out for this treatment and we were also the only non-UK passport holders on the flight - I wouldn't call that random. For me it wasn't that bad - spending five minutes in privacy with a lovely young lady. She did commend my shirt tast and hadn't it been for her hi vis vest and the uniform I would have asked her out for dinner strait away
In the UK I have only been approached by the police twice - once outside Terminal 4 at Heathrow and the other occation was on the southside at Manchester. The threesome at Heathrow came out strong, but I ended up with "a good luck with the hunt" and the team leader admitting he was one of us. At Manchester it was a bit different. The southside is patrolled by police from Cheshire, and my friend's comment after this short interview was: "That's the worst intelligence gathering I have ever experienced - and I should know with my intelligence background". We were allowed to continue out hunt for the perfect rotation shot