Self-storage group Big Yellow reported a 6% drop in quarterly store revenues but said trading conditions have continued to show an improvement.Total store revenue for the first quarter ended 30 June was £13.5m compared with £14.3m for the same quarter last year, but revenue rose 1% from the quarter to 31 March 2009.The wholly owned stores in the group increased occupancy by 56,000 sq ft over the quarter to 1,788,000 sq ft at 30 June, down 2% from 1,819,000 sq ft at the same time last year but up 3% from 1,732,000 sq ft occupied at 31 March 2009."Following the final statement in May, trading conditions have continued to show an improvement with a pleasing occupancy performance in June," said chief executive James Gibson."We anticipate the usual seasonal slowdown in the Autumn and continuing cyclical uncertainty but remain more cautiously optimistic," he added.