G-BU: I wish I could find my 3822! I remember other T21s at Sealand were WB993 (the first one I ever flew) and XN157. We only had one T31, which i never flew. A Swallow single-seater appeared for a week or two and was strictly for the instructors amusement.
They certainly were happy days. I remember rounding up sheep in a Land Rover before flying could start each day. The gliders lived overnight in an enormous hangar, which apart from the space left at the end by sliding the doors for the gliders was full to the roof with crated Canberra wings. There was a black-painted Sea Hawk outside the hangar, and at the North Camp a rather sorry-looking Spitfire.
Security was non-existent. One day it was drizzling when a few of us arrived before the instructors: we pushed a hangar door open far enough for the smallest cadet to squeeze inside and find the big cranking handle which operated the hander door mechanism. We then waited inside the control caravan parked in the hangar until an instructor "officially" opened up the hangar and then we quietly appeared, mingling with the now rather wet cadets who had waited outside!
I think my longest flight was about thirty minutes, thermalling over the John Summers steel works with an instructor called Tyson. Other instructors I remember were Westaway (my own instructor), Chaplin (as already recalled in earlier posts) and the CO I think was called Stanford-Smith, who sometimes flew with his Jack Russell terrier. I was sent solo by the CO: I seem to remember that there had been a halt to solo flights for some time after an accident at another school and I was the first to solo after the ban was lifted.
I feel oddly privileged to have enjoyed flying in the early seventies (and at the RAF's expense) exactly the same aeroplanes (T21, T31, Chipmunk) that cadets would have been flying in the early fifties, well before I was born. And of course those same planes carried on well into the eighties (and nineties, in the case of the Chipmunk).
How lucky we were!