Thanks to all those who have contributed to this forum. I have had the message servo restricted several times and message went off, me thinking all ok!! until message appeared again and and ABS was kicking in when driving. Found this forum and it was central to me sorting issue, changed (2 minute job) said sensor having got it sent from Phil at Cardiff Audi parts direct. All appears well now, no warning messages and stop start working and hopefully ABS saved!! Again a big thank you to this forum.