After a fair amount of searching / thinking / indecision, I believe I've found the right bike (motorcycle) so took the plunge and I've handed over the money.
'Peach' is a 1978 BMW R100S who needs a little work and a bit of TLC to bring her back to prime condition. Here's a camera-phone picture:
The previous owner is moving back to the US and wanted her to go to a good home - so that's what I will try to provide.
The panniers (Siebenrock, you can see one in the foreground) are tardis-like: you really can get a lot of stuff in there.
There's almost a year's MoT but no tax (fair enough as the owner won't be here much longer) and I will need to attend to a few practical things before riding long distances, but most of the remaining work is cosmetic. The R100S should have a bikini-fairing - this link is to a picture showing what Peach should really look like, but I'm not too concerned about that. At some stage I'll probably find and fit one.
I've never owned a BMW but always been attracted to these bikes: there is something very appealing about the simplicity of the engine, the feeling that you really do stand a chance of being able to do most maintenance yourself, and of course the overall build quality. The owner included the Clymer manual, toolset, complete set of spare bulbs and some other bits and pieces so I reckon this was a great find.
The owner is a great character and we spent quite a while just talking and drinking tea. The bike has a nice back-story, plus his parents owned BMWs too and there are tales of how they got on their 1965 R-50 (a wedding gift) after changing out of their marriage clothes into denim, and headed across America from NYC to California. Their children subsequently 'grew up' on the back of that one.
I really enjoyed meeting and talking to Walter - I'm sure we will stay in touch and he'll get to hear about my adventures with 'his' bike.