mpg td5 disco??

I recently done a run to Black pool, 70 mph with cruise control on and air con on there, stop start almost all the way back on the m6 but did hit 70 a couple of times,air con on, and i got 29mpg. I still have the cat and the egr and no remap. I am quite pleased with it so far, plodding around town i am getting 21mpg, Its a lot better than my 4.6 was
Mark