hi,
I drove Mazda 3 from Jan 04 to about 2 months ago (traded up to 6) the 3 is a fantastic car to drive, although mine was a 1,4 petrol and could be a little sluggish away from the lights, but once into it's stride has very few equals in its class (wife has a Focus, Mazda is miles better) I never had any trouble with the car and clocked almost 60k, Although I can't vouch for the diesel version I would definitely recommend the 3 as a good car. Try to get at least the Touring spec, much better than basic and it'll help when you look to trade in.