The 1.9 TiD engines are part of a joint GM/Fiat Group development, so cover Vauxhall, Opel, Saab, Fiat, Alfa and probably Lancia too. They’re widely used and mechanical spares are widely available (but be aware, Saab did some tweaking of their own) but not frankly the most reliable of engines. Cambelts should be changed religiously in tandem with water pumps, and there also can be inlet manifold issues, plus a tendency to go through alternators, dual mass fly wheels, and ERG(?) valves. They go very well when they go, though, especially on Saabs, and the TTiD variant you’re considering is the cream of the crop – sh1t off a shovel and better CO2 and fuel consumption too.
Re spares and repairs, yes it is true, Saab UK have now become a spares importing business, but it’s far and away best to use a Saab specialist rather than an ex-main dealer. They’re cheaper, way more knowledgable, and generally have better integrity. Saabflight in E Sussex, 2-Stroke in Herts and Malbrad in Yorkshire are all outstanding, but there are about 50 others around the country that are worth seeking out.
General build quality is not what it was before Saab were taken on by GM, when Saabs were bullet proof mechanically and in terms of bodywork – think how many classic 900s and 9000s you still see around. Sadly GM contibuted little other than their own mediocre parts bin, so as well as the mechanical issues listed above, modern 9-3s and 9-5s have quite a few electical problems plus the suspension is more fragile these days. However, they still are just about the most comfortable cars in the world, and feel (to me at least) very involving to drive.
I’ve got a 55 reg 9-3 Sportswagon which is on 152K miles and racking them up at the rate of at least 30K a year. I plan to keep it until at least 200K.
Oh, and finally – the 1.9 TiD engine is no great lover (along with other modern more spohisticated diesel engines) of supermarket fuel. Too much secret biofuel additives (up to 15%) means that you get biochemical reactions in your tank, which gets full of algae-like gunk and everything clogs up. Can be expensive in terms of particulate filters etc.