Nearly one-third of new Windows Phone owners in the UK were poached from rival platforms, according to new sales estimates.

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Windows Phone devices are now selling in "serious quantities", with 700,000 new users added in the past year in the UK, the WPP market research firm Kantar reported on Monday.

During the three months to the end of January 2013, Windows Phone, spearheaded by Nokia's Lumia 800 but also the third most popular WP device the HTC 8X, accounted for six percent of the UK's smartphone sales, up from 2.4 percent in the same period last year.

iOS and Android still dwarf Windows Phone, with 30.6 percent and 56.2 percent share of UK sales respectively, but Microsoft's platform appears to be consolidating its position as the third player. Kantar notes that 30 percent of new Windows Phone owners were converted from other platforms.

New additions to the UK's Windows Phone user base were made up of 17 percent from Android, six percent from RIM and two percent from iOS, while 26 percent switched from Symbian — and 47 percent were first-time smartphone buyers.

"The fact that nearly one in five new customers switched from an Android device should give Microsoft, and its partners, confidence that its OS has what it takes to bring the fight to more established platforms. As almost 30 percent of its customers switch from rival OSes, the worry that Microsoft will have to rely on attracting the dwindling pool of first-time smartphone buyers to drive future growth is reduced," said Kantar's global consumer insight director at Kantar Worldpanel ComTech, Dominic Sunnebo.

BlackBerry's share of sales has declined in the UK from 15.7 percent last year to 5.8 percent in the current quarter. But these figures do not include its latest BB10 device, the Z10 , which launched in February and is proving popular, according to BlackBerry .

Windows Phone is now the third most popular-selling OS in the UK, Germany, France, US, Australia, and Italy, where it made up 14 percent of all smartphone sales for the quarter and is snapping at the heels of iOS, which comprised 21.5 percent of sales.

In China, Symbian remains the third most popular OS with 3.5 percent share of sales, followed by Windows Phone with 1.2 percent. Android leads in China with 71.5 percent of sales, followed by iOS with 23.2 percent.