Citroen Berlingo engine cuts out

For the cutting out fault I'd be looking for an intermitant bad contact to the RPM sensor,
It's mounted down the back into the top of the diff on the gearbox,
Well actually where the off side drive shaft enters the housing that bolts to the diff.
Only thing down there with a wire harness.
Wiggle/tug the harness when running to get the fault to happen,
And check the harness isn't stressed,
Engine movement when cornering could be enough to stress the connections.
As to the speedo I'd run a Lexia diagnostic global scan for stored faults first befor pulling anything apart.

engine speed sensor is at front of engine.The sensor in the diff if there is one is for vehicle speed

Whoops!
sorry I guess I was thinking of diesels.

But taking Paulione's comments into it I still would be checking the engine wiring harness.