I'm not a proffesional, but, I know a man who knows a bit about these things and he doesn't think you need permission.
But, and this is a big BUT, you do need to ensure that you have supported the joists, above the wall before you start demolishing any walls.
Failure to do so would probably result in a structural failure.
It is strongly recommended that you employ the services of a proffessional for this sort of job.