not able to advise on "other" posts within ATC but, I'm sure others can correct me, the 28ish cutoff is a NATS thing. Might be worth talking to your local non-NATS airfield or, if you have the money, put yourself through the courses yourself, then try for a job.
Also, I always understood that the cutoff for NATS could be waived under certain experience circumstances.
Perhaps someone else could be more enlightening.