On a cable, the difference between 110 and 230 is negligible. The thickness of copper is less than 1mm, and by less I mean nano.
The voltage only makes a difference on whatever is receiving the electricity. Which is why so many rechargeable stuff, is the same country to country, only the pins change.
Bat changing pins n pin holes (a lot of extension leads now use a universal hole pattern) and the only difference is the plug that goes into the mains... Nothing else changes.
It's always best to use a 13amp fuse on a multiple extension lead, due to the possible draw of electric.
