quoting:
I have a 20W lampballastunit (from an energy saving lamp) that I would
like to drive 2/3 9W lamps with. I was about to simply run the lamps in
parallel until i realised the orginal lamp was a 4-wire lamp, but the
new lamps are only two-wire. So, before I make a mess of myballast, or
myself, i thought i'd see if anyone here had experience with them?


Your 9W lamps have starters built in to the base for use on non-
electronic (magnetic) "preheat" ballasts that use starters.
Fluorescent lamps will not work in parallel, only one lamp will ever
light. Your main problem is the starters is that they just aren't
used in electronic ballasts, and if they do activate, it's a high
current draw on the ballast that wasnt't designed for it and you could
blow your ballast.

A simple preheat ballast has only two wires attached to it. If you
indeed have a preheat magnetic ballast, then you can try the lamps in
series, but I don't think the starters will activate because the
voltage would be then too low as they weren't designed for series
operation.