Thanks rossco. I have a little more information that will hopefully change things and as a mechanic, maybe you can confirm. One of the first questions the various places I have taken the car to is "is it serviced regularly" and as I ensure this is done annually, my answer is "yes of course". On Saturday after writing the above post I went back to the garage that changed the hose and asked if they knew of any turbo specialists and they said that they thought they had checked everything and again asked whether the fuel filter had been changed which I responded "yes" to.
On coming home I decided to check the service schedule in the manual and made a bit of a discovery - for the first 2 years of servicing (by Dodge), rather than completing the Diesel schedule section they had been stamping the 2.4 litre petrol section. As a result of this, the people who serviced the car after continued on this schedule and as a result, the fuel filter that is supposed to be changed every 3 years has never been changed (the car is now 8 years old). In addition, the accessory belt that is supposed to be checked and replaced as necessary every 2 years has never been changed and finally the timing belt which should be changed at 60,000 miles or 5 years as you have probably guessed, has never been changed.
I've got the car booked in for Friday to have these 3 items replaced and I'm really hoping that the fuel filter is the culprit behind the jolting and overboost error (I'm hoping that it isn't really an overboost but when there is insufficient fuel underload due to a dirty filter the car is just making it's best guess). I have to get these things done anyway, but do you think the filter could be responsible for my problems and I have half a chance that the new one will resolve them?