I had exactly the same model (Focus 03 plate 1.8TDCi I had it from new it was 4yrs old with 22K on the clock and up to then was perfectly OK) with exactly the same characteristics, and once in a while it would not even start and had to be towed into ford dealer.
The first bill was £1922 and this included all the items youve had plus a new diesel pump etc.
A week later the car showed exactly the same problem. so it went on.
This issue ran and ran for some six months I did get some money back off Ford via the customer relationship centre who were generally hopeless and tried to 'lose' me a few times. but to get that money was a nightmare .
Eventually after six months of a nightmare It was towed yet again Xmas 2007 to the ford dealer who wanted to treat it as a NEW problem
I am a carer and need a car so I at that point traded it at book value for a 1.8 (this time petrol) Focus.
I am very sore over the way Ford treated me and remain amazed that over 6 months the Ford dealer could not solve the problem and let my car go to auction rather than sell it again. (once they had it in for 5 weeks)
I had no choice at the time to trade for a ford given my old one was broken at the dealers but I will NEVER buy a for, and will look to trade out of Ford as soon as I can.