Everything I have read doesn't indicate that the 2.0TDI unit is a duffer, quite the contrary. What is actually wrong with the 2.0TDI units?
They are noisy, reasonably unrefined, clatter like an old van and deliver most of the power an irritatingly placed lump over about 1500rpm tops. One minute you claim you want the performance of the ST220, now because somebody 30 seconds down the road has a TDI 140 suddenly that doesn't matter?
I'm not saying the Passat CC is a bad car - I don't really like them personally but they do look nice - I'm saying at least buy a decent CC not a bottom of the range one. There is not exactly a shortage of Passats on the market, you are spending £15,000 so it's not exactly a load of effort to perhaps go a bit further and find one worth buying with a decent engine - the 2.0TFSI is the pick of the range, decent performance, smooth, quiet, reliable, unobtrusive and reasonable economical. If you are absolutely convinced you need to throw an ST220 in the dustbin for 500 quid and buy a £15,000 car to get 'good MPG' then make it the TDI 170 rather than the TDI 140.
I always had you down as somebody who was quite methodical and rational yet you appear to be about to buy probably the least appealing car in its range simply because it was the first one you found on Autotrader and happened to be local. Don't do that. Travelling for a car like this is not a chore as its unlikely any of them are sheds as they are too new. Spend an hour on the VW approved website.
30 seconds on Autotrader has turned up these two, I dont know where you live but I put in within 100 miles of Southampton:
http://www.autotrader.co.uk/classif.../postcode/so155ab/radius/100/page/1?logcode=p
only 9k miles which appeals to your obsession with low mileage. Decent engine, great spec.
http://www.autotrader.co.uk/classif.../postcode/so155ab/radius/100/page/1?logcode=p
More miles but a VW Approved Used Car. They'd probably even deliver it!
And if the obsession with MPG really is a priority, a nice spec 170:
http://www.autotrader.co.uk/classif...rds/170/radius/100/postcode/so155ab?logcode=p
Don't buy a 140 Passat, its the automotive equivilent of wallpaper paste.