THE Gunne agency is to offer for sale by private treaty almost 23 acres of development land and a period house beside the site where Isle of Man businessman Albert Gubay is to develop a £50 million marina and leisure facility at Greystones, Co Wicklow. The agency is not indicating a guideline price for the property, though it is estimating that the five-bedroom period house and out offices are valued at between £250,000 and £300,000.