Storage firm Big Yellow Group said it enjoyed a "robust" quarter with a particularly "strong" June.Annualised store revenue, for the 51 wholly owned stores, rose 9% to £59.8m at 30 June 2010.Total store revenue was £14.4m for the quarter, up 10% from the same quarter last year. The 51 stores achieved an average net rent per sq ft over the quarter of £26.75, 4% higher than the same quarter last year but down 1% from the quarter to March 2010 period. The group said this was because of a significant increase in the number of new customers who benefit from its standard opening offer.For Ten Big Yellow Limited Partnership stores, annualised store revenue rose 255% to £3.9m at 30 June 2010."The Group has enjoyed a robust quarter with a particularly strong June. We expect reasonable trading over the next few weeks before the usual seasonal slowdown from September," said chief executive James Gibson.