At Heathrow and West Drayton, where I worked, the ATSAs were a hard-working, professional, good-humoured bunch for whom I had great trust and admiration. At smaller non-NATS units "ATCA" is likely to be the tea-boy. If you go for a job at a non-NATS unit make absolutely sure you know what you are letting yourself in for.
I worked at a very busy non-State unit once and the single ATCA worked the GMC frequency unsupervised, with a Student's Licence, took pressure readings from the barometer and converted them for QNH and QFE, maintained the tape recorders remembering when to run downstairs and change the tapes, maintained the official airfield log of every movement (over 1000 on busy days), wrote Flight Progress Strips for IFR traffic, answered all telephone calls to ATC and got clearances from LATCC... and all and all and all... oh yes, he'd get our refreshments and run errands. He had Sundays off... I've probably only covered half of what he did. He was truly superhuman but was treated appallingly. He later joined NATS and must have thought he'd died and gone to Heaven.