Regarding the RN as an Aircrewman you are not too old, A recent fella who applied but failed Grading was 33, You could either join the RN or RM in another trade, before requesting to transfer to Aircrewman, specialising in either Commando role or Anti Submarine Warfare role, both on Helicopters. There is a plan to allow direct entry in the near future for the ASW specialisation only.
Of the three services you may wish to consider this as an option. The training pipeline is much more swift with a great deal of emphasis placed on single pilot operations and Navigation, including DR.
PM me for more detail.