Hi Andy.
I'll start by commenting on the end of your thread, I have my Maestro T-Shirt, hat, sunglasses and drinking boots already for Classics on the Common this afternoon. There is a chap who the past 2 years has taken one of his V8s (he has a rover 75 and a ZT version) so there should be a car to view. I'm not driving.
As you're getting the 260 as a weekend car you shouldn't have any major problems as long as you'll never be in a rush to get things fixed. Most parts are available if you search round and use the forum. I have frequent niggles but I think with any modern car at 15yrs old that would be the case. One week it's an air bag sensor, then an ABS, then a leak in the boot, corroded brake pipes, failing fuel pump, now a slight leak from the diff... Mine has done over 120k miles tho.
BUT, when you get in, start the engine the smile it puts on your face is most definitely worth it. I also drive a VW T4 (family wagon) and a rover75 estate, which make the 260 feel nice and fast when I do drive it. There won't be many more petrol cars never mind V8s!
The one thing I would check is the radiator fan set up, make sure it's the latest (I forget the exact set up but I think you want the one with the visible resistor), a failed fan cost me an engine.

Cheers,
Ian