Funny you should say that as my other car that I still own is a 2014 Volvo diesel which i have been doing circa 8k a year in without issue. Its a Peugeot/Citroen PSA engine. I am aware of the head gasket issues with the D4D's so i suppose I took a chance as I didn't actually need a diesel but couldn't find the spec I wanted in a petrol. Mine is a sport so I'm led to believe it has different ratios to the SE and doesn't seem to suffer from the 'weird gearbox issue' that I can see. I'll keep on top of maintenance, take it for good long run once a week to let it regen and see how it goes, have RAC cover to get it lifted if required.
Would be interesting to see the stats on how many 220ds were sold and what sort of mileages people have managed to get without head gasket problems just to put things in some sort of perspective. There are review sites online that do have some good reviews and it people are more likely to leave a bad review than a good one. Seems to me there are so many variables on why these things go wrong that it is hard to point to one exact cause.