Can't think offhand what FISO airfields there might be in Yorkshire - most appear to be A/G or Safetycom. I'm afraid I'm not in a position to assess what FISO jobs might be around either; you tend to retire when you want rather than at a set age, although in my present situation, some people are getting 'second strings' such as gaining ATPLs or instructing as well as 'second' jobs outside aviation, so if this is the norm, you might find somewhere which is only part time.
It's certainly useful to get an A/G Certificate as if you get chance to use it, you will be able to understand RTF exchanges much better when (not if) you become an ATCO.