Since you don't state the capacity of the tank - only giving a price which is variable - its difficult to comment on the economy you were achieving.
Diesels are very economical, but can be lumpy and slow, while the new Trajet looks the part I'd check the year and safety of the particular model you choose.
I seem to recall that earlier models had a poor safety result in the NCAP crash tests, but I could stand corrected on that.
We tried a Ford Focus C-Max this year on holiday and it was perfect for our needs.
Two adults and a nine year old in perfect comfort, motorways and town trickling were no problem, even with a manual.
VW's DSG auto box gives both quicker shifts AND more economy than a petrol model and the 122bhp TSI DSG is a serious contender here.
If not that, then a Nissan Qashqai 1.5CDi might be a good choice - it seems to be one of the few cars being bought in any quantity in Ireland this year.
FWIW
ONQ.