I have had this problem a few times at various garages. Sometimes to the extent that the pump turns it self off and I have to pay for one lot of fuel and then continue to fill up again. A man at a Shell Garage with a
MCS said he uses a length of plastic fuel tube to go down the side of the nozzel to let air out of the tank so the fuel flows in easier. I haven't tried this myself yet, but I might give it a go.