it would seem ok for slow town driving, but over longer distances 35 is pretty poor. to put it into perspective, mine is the 143, and last week, over a very steady motorway drive of about 200 miles, i averaged just under 65mpg using the v power diesel. on the regular diesel, i did the same drive and got about 57mpg, so compared to yours, im doing nearly double... mine has 82k.
maybe it needs a good service, as in injectors cleaning, and would it benifit from a few good hard runs now and again? i know a lot of other diesels certainly do.