Some questions on an extension

[Probe]

Hi,

We have an exisiting conservatory in a north-facing garden which we would like to replace (and entend) with a single storey extension.

Several questions here!:

1. We are semi-detatched so the east wall would (ideally) be tight to the boundary. Would this require planning permission?

2. There is an existing sewer inspection pit which would end up being inside the proposed extension. Would this have to be relcated?

3. We would like to have as much glass as possible in the north wall. Given that the east and west walls would be brick cavity and the roof would be insulated to the highest (realistic) standard, is there a ratio of room volume to area of glass I can work to?

Thanks