Investment group CLS Holdings said it had made a strong start to 2015, boosted by lower cost of borrowings and steady occupational demand.The FTSE 250 group said its overall vacancy rate was 4.8% of rental income on 12 May, a 1.8% increase compared with the end of 2014, after 4.421 square metres of former development stock was made available for letting.Meanwhile, the weighted average of the cost debt declined 0.02% to 3.62% in the year to date.CLS said it was encouraged by performances in the market, particularly in France."I am encouraged by our letting performance, particularly in France, and by the interest shown in the recently-completed developments at 138 Fetter Lane and the hotel at Spring Mews," said group chairman Sten Mortstedt.Mortstedt added that the company was confident of building on its strong performances and retained a positive outlook for the remainder of 2015.CLS shares were down 0.54% to 1,850.00p at 09:04 on Tuesday.