Ford Focus 59 plate 1.8 petrol zetec model - strange noise

[prudishvicar]

My Ford Zetec 1.8 petrol car has been making a clicking noise when I pull away - the noise is like a solenoid switch engaging and seems to come from the engine bay. If I stop and pull away again - no click but if I switch the engine off and pull away again same noise. The click only happens once each time and will even do it in reverse gear. If i run the engine without moving the car there is no noise. I even jacked it up at the front and tried to identify the source by having a friend go through the gears once the wheels were off the ground but the car 'knew' the front wheels were in the air and the sensors were going bananas. Only way I can think of is to get it on a rolling road and try to identify it that way. I don't want to go near a Ford dealer as when it went in for it's first year service ( I reluctantly took it to them to preserve the warranty ) they damaged my undertray and left the oil filter slack and leaking oil. Can anyone suggest what this noise might be ? It definitely did not make the noise when I got it at first.