Going Through Security With Boarding Passes For Two Flights

In August I'm arriving into STN from HHN at 18:30, I'm booked on the 19:40 flight to Belfast City. I've taken the precaution of also booking onto the 21:45 FR flight to Dublin, in case I miss the Belfast plane (which can be a little late). When going through security, would there be a problem if I were to present both the boarding passes for scanning to the person at the entrance to the security area? Would I be better to just show the Belfast pass, then if I don't get on the plane, come out and go through security again, or will the security person, sitting at the junction of where you you enter and leave the domestic pier of the airport, allow me to pass into the main airside area (where all the shops etc are)?

What would the situation be if I were coming off a plane at Stansted at one gate and my next plane was departing from the gate beisde it, could I just go through the gate and board, would they be any the wiser? I called Stansted and asked them about this at one time, and their retort was that you must go out and come back in through security. The thing is when your boarding pass is scanned at STN does it register you on the computer, or does it merely show the security person what flight you're booked onto?

Yes, you must go out and in again to get yourself to the plane.
My friend was departing from Alghero and had 2 flights booked - one to Hahn and another to Weeze which was departing 25 minutes later. Just in case of delay - same reason like your one. He's written he's been asked why does he have two tickets booked? He said what the story was and passed with no problems.
To be honest, I don't believe they may ask you for anything. Why? When I was working at Dublin airport I saw few ppl doing 6 daily flights between Dublin and UK just for business meetings. So in British-Irish connection it should be very often case :-)

As amnesia has mentioned you will have to go through security all over again. At STN, once the security staff have scanned your boarding pass, this means you are "airside" on the computer. At the boarding gates they also scan the part they take off of you, this then cross references those that are "airside". If someone has checked in on-line, and has not been scanned once they have everyone that has gone through security, the plane goes.

If you haven't had your boarding card scanned, then you will be deemed as not being at the airport and the plane could just go. However, if you turn up without having the second boarding card scanned, I would imagine they would be asking you some serious security questions about why you had not been through security and a possibility of denied boarding.

Just be polite and explain what you said here and you should have no problems.

FR flights are that cheap you can double book!

Just to let you know that I did the flight from HHN, we arrived into STN 15 minutes early, the passport control queue wasn't too bad and the security one was very short. So knowing that I had the best part of an hour before my Belfast flight, I didn't bother to mention the Dublin pass to the guy checking the passes, knowing that I wouldn't need to use my "escape" flight. However my bag got selected for examination after being xrayed (for the 3rd time in one trip!), the middle-aged bloke doing the searching was very friendly, so I asked him about the going through security with boarding passes for two flights senaria, he scratched his head and said "that's is an interesting one", he went on to say that you should really go out and come in again if you miss your first flight. I was left with the impression that it would really depend on who you was checking the passes as to whether or not they'd scan both of them. Thanks for your replies folks, and thanks to Ryanair for having fares that low that you are able to book an optional flight.