Lack Of Power Misfire Focus 55 Reg 1800 Tdci

Hi There

firstly I must explain I am sure I have coursed this but have no clue as to what I have done. I will try to keep the story short.

A few weeks ago while re-fuelling I was a bit distracted and put about 3 litres of unleaded fuel in my 1800 tdci. The tank was empty so I filled the tank with diesel and with fingers crossed started the car. It run fine and didn't miss a beat "great" refilled tank again after 300 miles and all good until I got down to 1/4 tank some 2 weeks later car started to misfire and not rev, I kept car running and after a few minutes it picked up and was fine. I have had the same thing happen a couple of times in the last 2 weeks but tonight while traveling home it did it again but after a few minutes it didn't clear. it seams like it has a complete lack of fuel as it will not rev above 1500 revs above that and it misfires and you can hear the engine is flat it stays running but will not rev or pull I drove the last 6 miles under 1200 revs and it was fine but try to rev and its not having any of it. once home I just put the throttle on the floor and after loads of missing and juddering it cleared and started reving again but now I am worried about going anywhere as I don't know how it will run or if it will make it back.

any thoughts would be a great help.