Staffing business SThree reported a 23% increase in gross half year profit after an improved performance across all regions.The provider of permanent and contract staff said group gross profit rose to around £90m for the six month period ended 29 May 2011 from £74.3m in 2010.UK gross profit increased by 9% and non-UK gross profit increased by 34%. Non-UK now represents 63% of gross profit, up from 60% the year before.Permanent gross profit increased by 34% and contract gross profit increased by 15%.A total of 3,450 permanent placements were made during the six months compared to 2,842 a year earlier. Group sales headcount at May 29 was up 12% from the year-end and up 14% year on year. Sthree opened new offices opened in Sao Paulo, Doha and Antwerp and plans to open offices in Zurich, Luxembourg, and Chicago in the second half. The group had net cash of £47m at the period end. CJ