Border force have been cut to the bone and quite often have to rob people from the channels just to try and get the Q’s down.
The place is in a much turmoil as my old place.
I might be wrong but I would think the people telling you which Q to go in are either the airline staff or BAA.....Border Force are the ones who have to check your passport and are completely different.
I think the airline scheduling often doesn't help, recently at T3 had three big flights from major US cities all landing within 10 minutes of each other and with other Non UK/EU flights at the same time it really isn't rocket-science there are gonna be a lot of people to be processed...