I've actually just recently purchased the flat from my old landlord so have all the deeds/ boundaries etc fresh in my mind. Typical that this should happen just as I become the owner!!
Cannot find any planning application or approval online. I know if I report them they'll get a hefty fine, however, it's not my fault that they are completely ignorant to the law!
I think I'm going to go round and see how they react. If they're dicks about it I'll report.