Fitting of new front bumper with parking sensors

A bird made a hole in the (very flimsy) front grill. Unfortunately you cannot buy a Skoda grill alone you have to buy the bumper. Very annoying. The dealer had the bumper sprayed before they fitted it and when the car went in they said it was a two hour job. It turned out that they did not have all the parts because the parking sensors have some brackets that were needed. The paint is now flaking of around the sensors. Two questions: They ordered the bumper from the REG/VIN should it come with pre made holes for the sensors? (I've a feeling it didn't) and should they have sprayed the bumper before fitting or after fitting? It seems to me that as the sensors are matched to the colour of the car you would want to do them at the same time as the bumper otherwise you will have to mix paint for a vey small job. I am hoping the dealer will just agree to rectify but any information would be much appreciated in case I have to do battle.