Mine too Kevin,thats why Im stumped.Perfectly logical regarding the return line btw.I will do that. 
Having said that,I have heard several estate owners say that they behave differently to saloons when they have run out.
Mine gets quite sensitive to both pitch and roll once down to the last couple of gallons

had it cut out before now without the low fuel light on and a range of 45 miles on the MID

The pump lives towards the rear right hand corner of the tank so any combination of slope away from that increases the chances of cutting out quite significantly.

Had a 2.0 Efi Granada that refused to fire when the pump got weak. It used to do 400 miles every weekend, and nothing during the week. Went to drive it on a friday evening and it cranked readily enough, with fuel reaching the rail. It was only when compared with an identical car that the significant difference in fuel rail pressure became apparant.
Fwiw, my money is still on the fuel level, with the filter and pump following up. Rank outsider would be the crank sensor
