If I understand you right, you need our graphical tool to have a resonable performance in showing nodes and walk throu the tree. I am not recomending you a tool, but a design pattern "Flyweight" and a SAX tool for information retrival. 
Look at Erich Gamma & ... "Design Patterns" book.


> As part of a Business Information System (BIS) I am to create 
> a node tree of
> 
> up to 180,000 nodes which is then to be represented 
> graphically as a tool to
> 
> drill down into the BIS.
> 
> I have been trawling the archives but am yet to see a 
> definite solution to this
> 
> problem. Any ideas anyone?? Help would be appreciated even 
> with what maybe the
> 
> best parsing method and tool.

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list