Went to my dealer this morning for another attempt at switching on the TCU.
They had received a multi-page troubleshooting document from HT/HCSS (Honda Technical/Honda Connected Services Support) last week.
Great news they managed to switch on the TCU at the first attempt without the use of the TSD, same tech as before with no changes in method.
Bad news still can't set up MyHonda+, I think my account needs to be deleted and set up from scatch. At the very start of trying to set up MyHonda+ while not realising TCU was off unistalled/reinstalled app twice.
Called HCS and replied to email with info requested and now waiting for a reply, not expecting a quick reply as previous emails to HCSS on this issue have been taking 5 to 7 working days to reply (they work Monday to Friday).