Although Ali Bongo is partly correct, ATC and AATC (TG9?) are not the only jobs earning waivers for the NATS age limits; Fighter Control is also accepted as relevant experience. There are several ATCOs out there from the FC world, and at least one who is about to start.
What I find slightly odd is that there was one guy who joined NATS in the last few years who, although a member of the FC Branch, had never actually controlled aircraft. He was a Surveillance Officer. I believe that NATS accepted this showed an ability to 'read' a radar display and, presumably in concert with his aptitude scores, felt he was a good risk - they seem to have been correct in this assessment.
Although the opportunity exists to fly E-3s from the FC route, there is absolutely no guarantee, and I would suggest it is unlikely if you are on a SSC.
As far as the WSO to NATS is concerned, I have no knowledge of anyone going this route, though I am sure someone out there will be able to advise. Why not ask NATS for an opinion? Just bear in mind that they may change their rules by the time you come to join.
I would be dubious about your achieving success in (enjoying!) any Branch in the RAF if your reasons for joining are more to do with your future plans than what you want to do now.
Good Luck!