I have lived in and around the area for 48 years and today was the first time that I spotted this garden.
It is tucked behind a car park where I was parked today. More information below. https://havantcivicsociety.uk/havant-gazebo-garden/
How pretty! You must go back when things are in bloom to show us. It already looks terrific, but I imagine will be even better when everything is blooming.