Again, to help your understanding of reported issues similar to yours see this one and in particular the posts by "presience"
viewtopic.php?f=10&t=11785&hilit=tappets&start=0
Sadly, and like so many, this thread ends without feedback as to what was finally found/done to resolve the issue. But one thing in your thread that caught my attention when it said the trader had suggested he was going to give it service and given what is said on that link it may be worth finding out what oil the trader used in your car
Although its not my part of the world we do get good reports on here about Lockwood and Greenwood that seem to be nearish to you (via the AA?) for a reliable check.
http://lockwoodandgreenwood.net/