re your "different cables" query: on the day in question i.e. when the phone went dead, The phone was been constantly used so hadn't been left to sit for any duration. I didn't notice that the battery was indicating a "running low" status up to the power failure time (having said that this is only indicated by the common, to many phones, small battery icon in the top RHS of screen turning red or similar colour. Although I would usually notice it's colour change). I then tried to recharge it with the charger I always use but no joy. Following that failure I bought a new battery and it failed to power the phone when installed directly from the new battery's packaging. So I then tried charging it with the same charger I have been using all along - failed to charge. I'll see if I can borrow another charger to rule it out and get back to you. To your other comment re treating like a flash drive would there be a way that the battery circuit could be 'bypassed' to power the flash drive by way of opening up the phone to main board level by a technician with that type of level of expertise?
would you have the names of a couple of data recovery companies. I might yet check it out as a Plan B. Looking to purchase a universal recharger in the coming days to see if it was the charger and not the battery that failed.