Finally had some interest so, after three weeks sitting on the drive, I started her up without problems and got her ready. Took a 30 minute run to warm her up all fine, and the guys arrived to buy. Took one of them for a quick spin, including a solid accelerate from 30 to 70 in S mode. Part way through I though it coughed, and as I pulled up at the lights there was clouds of blue smoke!
Not entirely sure what went bang, but there was oil in the radiator filler cap, and a lot of smoke....



There followed a renegotiation on the price - but in the end I figured I really hadn't the stomach to take her up to MRC for a re-build, or a new engine.

So, that the second engine I have destroyed in 11 years and 220000 miles

Better treat the C7 with some respect!