Twitter made a profit of £17,000 in the UK in 2011

"Twitter, which is inching towards an $11bn (£6.8bn) US stock market flotation, posted profits of just £16,500 in the much-delayed maiden accounts for its UK subsidiary.
It is too early to tell, however, whether the microblogging website will adopt the kind of financial structures favoured by other internet firms such as Google, Amazon and eBay to lower their UK tax bills.
Very little is known about the finances of the San Francisco-based group, which is incorporated in the US tax and secrecy haven of Delaware. The business is estimated to have taken $288m in global advertising revenues last year, according to the research firm eMarketer – a figure that is projected to rise to $545m this year and $807m by 2014.
[...]
Abbreviated accounts, covering the first seven months of Twitter UK's life, were only signed off by Ali Rowghani, the US group's chief financial officer, last month. The three-person board consists of Rowghani, Twitter chief executive Dick Costolo and the site's group counsel Alex MacGillivray – all of whom are based in San Francisco. The UK firm's registered office is given as that of its solicitors, Baker & McKenzie."

Source:  Business Insider, 9th January 2013

Note - This was 2011; the UK operation only opened that year, so any profit is impressive