I have just been to mothers for dinner, left at 6 and car was fine just drove home now, stopped off at tesco for some milk etc car was fine. Got back in, turned engine on started fine, drove off and noticed the engine management light had come on and i then checked what it was in my book and it said "glowplugs" ? what are these or what do they do and are they expensive? it says in the book to seek technical assistance immediatley?