The current UK corporation tax rate of 20% is the lowest rate in the G20, the 20 major trading nations. This rate continues to apply until 2017 when it has been announced that the rate will be reduced to 19% and then 18% in 2020.
This appears to make trading via a limited company more attractive but note that there are significant changes to the taxation of dividends that take effect from 6 April 2016.