Compression Problems With My 96' 528i

[nedofthehill]

I have a 1996 registered 528I which appears to have a compression problem. IE it is lacking it!. I have been told that the early E39 all had a problem with the Aluminium block and BMW replaced many using a factory recall. The History of my car states that it has had a replacement block which should mean this problem should not be happening but I have been told by a local BMW specialist that until mid-98 the replacement blocks had the same problem. If this is the case and the block that was replaced in my car is one of these what do you think the chances are of getting it replaced again?. It now has 120k miles on the clock and the new block went in at just over 30k miles so this engine has done 90k miles. It has a full service history and has certainly not been abused as I know the two previous owners who I would liken to Morgan Freeman in 'Driving Miss Daisy'
I know the obvious place to start is with the local BMW Dealership but I wondered if any one else has had this problem and were they started. I realy cant see a dealership wanting to push this with BMW UK on my behalf. Am I better off going straight to BMW? Any advice would be greatly received.