All I can find out, is that its from a German manufacturer, and there does'nt appear to be any UK stockists of it so I'm buggered on that front.
All I can suggest mate, is that you test from the plug top/s and work your way back towards the lamp holders via the ballast/tranny/ignitor/starter etc until you no longer get 230v on your tester. If you havent got 230v at your plug tops then obviously just a fuse that has gone which could easily blow from lamp/ballast failure if it was a dead short!
TBH tho it should'nt be too hard to find.
Are all the wires and connections accesible. If so, once you test for voltage then test continuity of each wire to test for breaks.
Could be dirty/corroded terminal from moisture?
How about a few pics of it mate [close ups too].....connections/ballast etc