That's not a native ladybird, it's an invasive species commonly known as the Harlequin Beetle or Harlequin Ladybird (Harmonia axyridis), they're threatening native ladybirds.

There's some infor on it here: http://www.ladybird-survey.org/harmonia.htm

They're very pretty but they're thought to threaten our native ladybirds, being introduced to the UK and North America from Asia by accident. I've seen one in my own garden and while they're very pretty, I am concerned that I shan't see as many of our own humble ladybirds if they do take hold, which they seem to be.