According to Experian Hitwise, Google's share of the UK search market has dropped to below 90% for the first time in five years.
Search via Microsoft sites, including Bing (which is the default search engine for Windows 8), increased market share by 0.72% (to 4.71%) but Google remains the search engine of choice for the vast majority of searchers. As Experian states "there are 18 times more searches conducted on Google Sites than on all the other search engines combined"
Sources: Experian and ITProPortal.com