You need to have BT Internet to get BT TV.
You would have to move your services over to BT.
Cannot have a dish on building lol, currently jus normal freeview.
You could buy a Youview box which will work with any provider. That would give you the normal SD plus HD Freeview channels.
Ther are also built in apps which allow access to catchup, and subscription services via your Internet connection.
You would need an unlimited download allowance to use that.