Presumably your car is out of warranty. If it has been serviced to schedule by a Citroen dealer you may get some goodwill contribution. If no warranty and no goodwill on offer then you are short of options. If you are in the AA or RAC you can explain to them your problem and they may offer an engineer to examine the car and the repairs and be able to ascertain the exact problem. If you are not with AA or RAC you can still hire them or an independant engineer to examine and report but that will cost you up front. You also need the old pump so it can be examined too. It may help to explain your concerns to the Service Manager at the dealership. Make an appointment to see him and explain calmly what your concerns are, at the very least he may offer you some discount to dull the pain. Unfortunately cars parts do fail and sometimes you just have to bite the bullet. At least the repairs will have a warranty for at least a year. Best of luck. Concrete