Perhaps those still in 'blue' could advise, but to be a RAF WO in your early 40's is still good going - remember, there is no WO2 in the RAF (Flt Sgt equivalent).
Furthermore, the Technical trades have the Chief Tech rank between Sgt & Flt Sgt; this represents an additional hurdle to their promotion prospects, especially significant when the age/rank/retention spectre looms. The non-technical trades do not have the burden of this additional rank (hunkers down now to await meat-seeking missile salvo from all directions).
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HB - you've been gone too long; we got rid of Chief Techs 5 years or so ago. You might see a few around, but we're not creating any more (for the reasons that you outlined).
The Flt Sgt equivalent is (and always has been) Staff Sergeant or Colour Sergeant - WO2 doesn't have an equivalent, although the Army will claim that all WOs are the same!
43 is generally pretty good for WO - but each Trade is different. Good for Eng, not sure for Medics, average for Int, Master Aircrew different again.