Section F1 Page 9 of the Building Regs says you need ventilation (several different methods allowed) if there isn't an opening window...
http://www.odpm.gov.uk/stellent/groups/odpm_buildreg/documents/page/odpm_breg_60...I'm not sure about the need to notify BC. I think altering the stack might make it necessary if not the excavation..
Not sure about Planning Permission - I can imagine that if it's at the front of the house and/or you are in a conservation area then it might be necesssary.