I went in to LGW in September twice--once early Tues. morning on CO and the second mid Monday morning. The early morning--took 1 hour 30 min to get through immigration--longest time I have ever had by an hour. I was in BF--but no help. I attributed this to the move to the North terminal as previous trips into South terminal (at least 20 times in the last 5 years) were again, all less than 30 minutes and most of the time around 10-15 min.

On the second trip, I "breezed" through in 20 minutes (non CO flight--but in to North terminal as well).

When heading out on the Saturday, the IRIS office was closed so I couldn't get signed up for it.