Thanks, HL. Will do. That's a big help.
[moan]
Slightly bemused by the need to show 'proof of your travel 'ex. Boarding pass, hotel reservation, train ticket...'
I rented the car. I showed my driving licence, passport and IB+ card. I paid. Ought to be enough. @:-)
Oh, well. The Avios will be useful if/when they finally turn up..
[/moan]