Tell us, what ballast are you using? did you need to use a converter to supply the light with 120v vs the standard European plug?
My money is on either your lamp is a 120v thus drawing half the amps through a 240v system and throwing off your meter, or your meter is bad, or lastly you bought yourself an uncommon 200w ballast, or perhaps your ballast is only working on half strength.
Time to open up those dusty electrician coursework books and find out where your messing things up.
A simple google search should be enough if you are having trouble finding your old books. Cant do it for ya, late for work.