I've had a 2003 5spd Aero Estate for the last 2.5 years (bought as a Temp. stop gap until my SX was back on the road...) & have done approx. 35K in that time. The only diesel to specifically avoid was the 3L Isuzu derived one, for the reasons already stated.
The ignition cassette started to play up, but the new-old stock one I bought for approx. £240 2 years ago from Neo Bros, has now done 30K @ stage 3+ (c) 310hp & is showing no signs of deteriorating. It's done two Weekenders & I don't treat it with kid gloves, but overall, apart from a tubby replacement needed after our Anglesey Weekender, blown on the hottest day of the year, I've enjoyed it.
Plus: Great load carrier, MPG good on faster roads (I get 35+mpg set on cruise at a real 70MPH), comfortable & quiet place to be, great ICE, far higher safety levels than the vast majority of that age/price, & the image is OK, not flash, & not frenchy/far east cheap, just about right. Seemingly invisible to the police.
Sub-plus: 20->23mpg around town, & even with the B8 shocks & sport springs fitted to mine, it is no joy in a corner. GM underpinnings.
Some of the above isn't relevant to a non Aero diesel auto, but the essential load lugging capacity, great value & general good build are. If it passes muster when given the basic checks all old girls deserve, I'd say go for it. Simply put, when I replace my current one, & assuming I won't wish to spend much on my second car, (SX will be my daily) I'll be buying another 9-5 estate.
R.