I would say mk4 golf tdi or passat tdi. Not keen on those fiestas really, I liked the one previous to that shape but I don't think those ones are a great buy for that money.
Get a Bora. You can get a fully kitted out 6-speed 115bhp for that money. A Golf of similar spec etc will be 3-4k
I get 60-65mpg as long as I stay within the realms of legality (ish). Even when I drive around my runway at 80-90 It never drops below 55.
Dont get the 150bhp engines as they tend to eat boxes, as do the 130s but not as often.
And also - stay VAG as it will hold its money.