I would like to build a roof terrace on my ex local authority leasehold flat. Lockdown has made me realise that zero outside space is no good for mental health! It's in a victorian conversion in Camden. I understand that I need planning permission, permission from the district housing office and to buy the roof from leaseholder services. It's a complex thing and I don't want to spend thousands on architects plans without understanding the pitfalls first. The person in charge at the district housing office wont answer the phone or emails! Does anyone have any experience with this?