Well i was gonna reply to agree that your take on this was probably correct, and i would never get my 2nd sub.
HOWEVER, MIRICLE OF MIRICLES its been sorted and my 2nd sub slot is open again
I appealed to "Betty" on the Heros Charge forum and she replied :-
Dear Leader
We will report your case to our production team and see if they would assign a developer to look into your problem. Thanks.
Best Regards
Betty
within hours the issue had been fixed.
I would suggest to anyone needing ingame support that the best route seems to be to contact ADMIN over on Heros Charge forums. Sending in support tickets on Tynon no longer seems to get any attention.
Thx to Kaisim and everyone else who offered advice here, i'm just glad to be able to continue playing for a while without a handicap.