What kind of mpg do you get over a short 1 or 2 mile journey?

Generally I get about 45-50 mpg on those sorts of trips.

Obviously the the longer the trip, the better the mpg.

Citigo Greentec 75ps

About the same for me, if I commute (6 miles) then that's about what I get. The longer and steadier the trip, the better the economy.

On a cold day and only 1 mile, I get as little as 25-30 mpg...

Yeah when I go to local shop about 1-2 mile I get 30-40 mpg

What kind of mpg do you get over a short 1 or 2 mile journey?

No idea - we walk, cycle or (if shopping) take a bus for such short distances!