BD7

Thanks for the link, v useful

I am looking at knocking down an existing old conservatory and replacing it with a single storey extension, which I want to make longer. I have a question re permitted development, which as from May 2019 allows 6m in length, and up to half the width of the house. My house is semi-detached, so I can go out up to 6m. However, the back of my house is L shaped, so my question is from where can I go out 6m, from point X or point Y on my diagram?