Thanks for the reply, I've found a eBay unit similar to mine here:
https://www.ebay.co.uk/itm/AUTORADIO...wAAOSwOL9alX14 and you can see the usb socket on the left hand lower side. Perhaps you, or someone else, can identify if it's a mini or micro socket.
As I stated in the opening post Misek says the FTDI cable is the only one it will work with at present. The phrase "at present" sounds encouraging. So I think my best bet will be to try some kind of USB adapter but also have a look through a box of "extra" connectors I've got up in the garage attic from Xtrons & my earlier Win unit, I might even have one for the Xtrons
Thanks for the link.