Big Yellow Group reported an increase in revenues during the third quarter of the year despite a fall in occupancy.The storage group said the period is "always a seasonally weaker quarter", with a decrease in occupancy by 103,000 sq ft compared to a loss of 120,000 sq ft sale time last year.However, revenue was up 13% to £21.3m.Big Yellow has completed the shell of a new store in Enfield which will open in April and acquired a new store in Battersea, which increases the freehold ownership of it portfolio and protects the group's position in central London.The company's chief executive James Gibson said he is looking forward to a seasonally busier spring and summer trading period."Looking through that, we believe the structural changes in London and other major cities, the barriers to new self-storage supply, the recent changes to stamp duty, reducing energy costs and continued low interest rates are all positive for self-storage demand," he continued.Shares were down 1.09% to 591p on Tuesday at 10:33.