1.9 desiel picasso Xara no acceleration engine still running?

Friday morning my 1.9 desiel Picasso due its annual service. Strangely car refuses to start. Mechanic comes to house to collect car. Saturday after service informed that new fuel pump fitted.
On the way home approximately 5 mins drive experienced power drop, car slowed right down no acceleration took 15 mins to get home.
Drove car round block three or four times seemed to be running OK thought it was just a sticky fault. Left to go up M1 car performing OK.
Approximately 13:30 80 miles away on the M1 car experienced engine power failure ie engine running but the acceleration died and car coasted slowly along.
AA were unable to determine fault other than the diagnoistics showed the Fuel pump as the problem.
Had to get towed home.
As the engine was still running I feel there is another fault can any one assist please.