hi I have a 57 fiesta zetec s and my powertrain warning light has came on flashing, when I start it beeps with a red light and says there is an engine system fault. I have just taken it into ford dealership and they tested it and said its my glowplugs but I never got it sorted because I was putting it through its mot. They also charged me £72 to upgrade some engine software before they could diagnose it? never heard of it before! anyway it seems to be starting fine but its like the car is in limp mode because its not as nippy as it is meant to be. I have been quoted £15 each for 4 plugs and one hours labour does this sound right or can I get them cheaper elsewhere?