Huddle, the three-year-old UK cloud collaboration start-up, has closed a $10.2 million B round from Matrix Partners and existing investors Eden Ventures and Huddle chairman Charles McGregor.

Huddle, which recently went cash flow positive, according to co-founder Andy McLoughlin, has already been through a $5 million first round. It means to use the new money to push deeper into the United States, which will entail quadrupling its current 40-man staff in the next year.

McLoughlin has just moved to San Francisco from London to head the effort.

Current customers, half of whom are based in the stas, include Procter & Gamble, Disney and HTC, as well as what the company says are tens of thousands of small businesses and freelance workers who pay anywhere from $8-$200 a month for the widgetry. Enterprises can pay $150,000 a year.

It’s also got partnerships with HP and LinkedIn. HP bundles Huddle with its business PCs on a revenue-sharing basis. Huddle’s gonna be looking for more OEM arrangements as well as direct sales.

McLoughlin thinks something might be worked out with Microsoft, some of whose technology underlies the Huddle platform, once a prospective SharePoint connector is finished. Huddle also uses open source technology.

People use Huddle as a secure workspace to share files, manage projects and workflow, control and distribute information, suggest and discuss ideas and hold online meetings, as well as connect with colleagues, customers, partners and suppliers. The company says it makes it easy to work with other people inside and outside companies, across boundaries and time zones.

It can be accessed online, on mobile, on desktop, via Microsoft Office applications, on major business social networks such as LinkedIn and Ning and in multiple languages.

Matrix general partner Josh Hannah, who has been named to the Huddle board, claims, “It’s not often we come across an enterprise software company that is inherently viral and has the potential to redefine how we work with each other.”

Huddle CEO Alastair Mitchell said: “If Facebook’s aspiration is to be the social fabric of the web, Huddle’s mission is to become its equal in the workplace.”