Have a look at a 530d. I know it's not 2 litre, but with an auto box they make a fantastic road trip car, and still does 40+mpg with 90mph cruising, and is just shy of 200bhp with masses of torque everywhere. They are seriously good cars, have a look on here for threads about them, I have been totally won over by mine, how is it possible to ENJOY driving an automatic diesel? .. I have done 16k miles since March in mine, it has been flawless.

The other point to consider is does your dad actually do enough miles to make a diesel pay? Less than 15k a year and it will not be any cheaper than running a petrol, plus the cost of diesel maintainance can be very steep!