If you don't want something that will break down, avoid an old French or Italian car
The Focus or even Fiesta route isn't a bad route to go down, at least anything on those is likely to be cheap and with plenty of choice for people to do the work. I wouldn't even worry too much about it being diesel. Older diesel engines just aren't as good as they are now and the fuel consumption isn't always that much better....
Also think about Hondas, Nissans, Toyotas and the like, Jap stuff tends to go on for a while!