Outcome: We upped the idle speed and made it to the ferry. Met a nice RAC man this side who had us in the road super smart.
Okay so we learnt lots from this one!
a. It was as far we can tell a fuel blockage. We think it was El cheapo gazole (diesel) from various supermarket chains. Clearly not all diesel is made alike and especially in French France! RAC said theyd had at least three call outs with bunged up cars spluttering off the ferry.
b. The very nice RAC man drained the filter a bit through the water drain cock underneath
Link: (finally found out how to access the fuel filter)) and that seemed to sort things out. we already had a tank of branded fuel in it by this time and topped up with UK diesel so we think it may be okay.
c. We'll be changing the filter anyway asap and I think will take a spare one away in future as well. This problem only took a few days and may three tanks of fuel to appear. If away for a while you may be getting through the filters!
c. Watch your RAC cover. There severe limitations on it which give them an 'out' as regards declaring the vehicle uneconomic to repatriate.
This may be obvious but I didn’t know about it.
€800 euro budget for repatriation to your door so if the vehicle is too far from the port you're looking at local mechanic.
If they can’t be arsed fixing it they could declare it uneconomic and recommend letting it rot.