Miles to empty dropping very quickly.

[Neil w]

Hi my miles to empty has started dropping like a stone . Theres no sign of massive leak to match losing 10 miles in 500 yards. Any clues?  

[Madogen]

Have you recently reset the average MPG?
The average MPG will be used to estimate the number of miles you have left in your fuel.  If you have done a lot of long distance driving with a high MPG figure, since reset and then doing some pottering around town, you will find that your estimated remaining miles will drop significantly.
I have found this, in my old 2.0TDCi Focus to go from as much as 500 miles to as little as 300 miles.