How many 240 volt fluorescent fixtures can I connect to a 30 amp breaker?
Sounds like europe?  Total Wattage divided by voltage = Amps  or Volts x Amps = Watts.  so 240V x 30A= 7200W.  I would personally not hit that 7200 total watts and have the circuit totally loaded.  so the wattage of the lamps is the determining factor as Niall said.