Part of the problem with immigration queues is that even though Ryanair do not recognise "connecting flights", people still make two reservations to connect at STN. As a result everyone is in the same long queue even though some people don't actually want to enter the UK.
Until such time that the airport is redesigned to operate in the same way as LHR and LGW this situation will exist. Somehow can't see this happening soon.
All very frustrating for us that want to get back into the UK asap on arrival.
A connection channel would please MAG as transits would get to their shopping mall in departures quicker !!