Jonno21, Thank-you for your prompt and helpful reply. I should have included in my original post that at the car hand-over to me the salesman did show me how to input addresses into the satnav system (so the facility was working at that time). My apologies for the omission.
Whilst your post information didn't have the exact answer to my vanshed sat-nav feature, you have, by default, solved the problem. Whilst I was aware that if I wanted to update the software I'd probably have to download an update onto a memory-card and input that into car's system, what I didn't realize was that the satnav programme itself was on a memory cadr. Doh !
When I went to investigate the location of the memory-card slot and found it was in the cubby between the front setas, I discovered that
the card wasn't fully home. A gentle push with a pointed digit and it clicked back into place, and all systems then up and running. (Although the slot is protected by a dust-cover, in my use of the storeage space I must have applied pressure to the cover and caused the card to pop up from it's home position. I'll be aware of that from now on.
Many many thanks for putting me on the right path. 10/10 for your help Sir.