Yes less current will be used as they pulse slower (modern dimmers) so there is more off time in the cycle, however it isn't even noticed so in reality your saving pennies a year. Now days there more for people that like dimmer lights. The old resister ones will limit current getting to the bulb so you save more but as said there not as safe as the newer ones and you know what Britain are like on H&S.
If your trying to save the planet or money then your better off using them annoying energy saving bulbs and turning lights off as you lease a room even if for a minute.
A study shown that the only light where its not worth turning off if your not in the room for a minute is florescent lights. If your out the room for longer then 127 seconds I seem to remember or (1:27min) then its worth turning off. All other old and modern bulbs stabilise quicker and well under the minute mark. The old energy saving bulbs that taken hours to warm up taken far longer than the incandescent to stabilise but as its a lower wattage it was cheaper to run.