Once you’ve identified the right team to be in touch with you are halfway there. You’ll need to find out it is not a planning issue, but simply a matter of landlord’s consent. If so, the ward housing manager should be able to grant consent for you to do with work in an email, with assurances from a surveyor etc. that the work is fine if there is anything structural such as moving or removing a wall, and with confirmation you will get building control done (potentially by self-certifying company doing the work). Changing the lease afterwards to reflect the work that has been done is your cost and takes a little time, but it’s all worth doing to improve your property.The council is very unlikely to refuse consent if it’s a reasonable change that is structurally sound and improves the property, so it’s more a matter of plugging away with the ward housing manager. Good luck!