How many moving heads of a 13amp socket?

[adam2]

I would advise against too much debate, speculation, or calculation as regards the current drawn by a dichcharge lamp.

Measurement is the best approach, and as others point out, Maplin sell a mains power and energy monitor very cheaply.

Provided that the lamps are struck one at time, then the starting current is less of a concern, 13 amp plug fuses are fairly resistant to starting currents. Remember that a great many d0m3stic appliances use a lot more than 13 amps, very briefly whilst starting, and that the fuse normally lasts the life of the appliance.

 

(the current used by an incandescent lamp is easily calculated, but for other sources including discharge, LED, and flourescent, measurement is the best approach)