A light at the end of the tunnel?
I'm not holding my breath, but following a very straightforward message from me pointing out that they'd continued to ignore the issue at hand (choosing instead to quibble my supplied info or to sidetrack to irrelevant issues) and that (un-rectified) the issue could constitute a breach of the Computer Misuse Act (1990), Seagate have finally deigned that my issue is of a severity that warrants passing on to their developers (quite what they did with the log dump and additional they already requested from me remains a mystery) who will now try and work out what's going on and if they think that it might be worth fixing.
They've also offered to provide me with a 1TB usb drive 'for my efforts' which is a nice gesture but not one that will prevent me continuing to complain if they don't fix the unauthorised network access issue on the personal cloud.
So two months and a fair bit of battling in I've finally arrived at a basic standard of customer support, hopefully their new positive approach will follow through and deliver the goods.