hi guys
my 1.8t (aum) has started to develop a deep rattle noise when the engine is warm and at idle it goes away with any revs

. it sounds like its coming from the around the back part of the engine bay or under the engine cover. i took it to a garage to find out what it was and the guy said that the sound could be a bad case of tappets. he reckons a service will cure it as my car is due for one anyway.
im completely baffeled hope its not serious
has any of you guys had any tappet problems? if so how was it sorted
thanks in advance ash