@DevilDamo
I'm pretty confident it meets PD criteria with regards to floor area/footprint, height, position, proximity to boundary. I've also confirmed with the local council there are no restrictions to my PD rights at this property. My main concern is the addition of widows and french doors to the side elevation and maybe the design of the roof (the roof will be pitched to the same angles as the existing roof, and using the same tiles - but it's double hipped rather than a gable)
The line within the town and country planning act is what's got me worried - "(b)the development must not include a window in any wall or roof slope forming a side elevation of the dwelling house". But this section seems to include other things which are contradictory to the rest of the document. I really have no idea.
I've spoke to a local planning consultant yesterday and hoping to hear back today. I'm planning to sell it next year so I want to make sure it's all legit. I've attached my drawing incase you're interested
Application Drawing Final 2.pdf