Thanks, Sjonnie.
Mind you, whilst the radio works brilliantly, I can't get a peep out of the music on the USB, even though every song is recognised in the "Local Music" section of the menu, but just plays...silently! Now I get it as to why people shell out hundreds of pounds more to buy a unit from a shop that fits them to your car!!
I'll have a go at the steering wheel controls over the week-end; I think I've identified the right wires, and the previous owner is helping me out with a harness which he used on his JVC head unit to make it work...not that I think it will be that easy, somehow...
I will have to start pulling out my hair soon, as it has already gone grey...