@Rob Cowell I have started to experience this issue with my 2005 120. Read the codes and I get the P0093 error code. Has yours repeated this issue since the change of the filter?
Doing some research brings up a variety of opinions and reasons. Typically my 120 if not left to idle for a few mins before driving off it will go into limp mode, especially on colder mornings. Mrs seems to also think this happens more frequently when the fuel in the tank is low. Some suggestions seem to indicate that cheap diesel could be the culprit, so at next fill I will change away from supermarket cheap as (I have always used this from new, now at 117k), to having to do something with the SCV and replacing injectors.
Could also be dirt in the tank or a air in the fuel system.
I serviced it recently with new oil, air and fuel filters, and oil, bit it still does it.
Any thoughts from anyone?