Link-detached single-story extension permitted development

[Ponja]

I've done my best to wrap my head around permitted development but still struggling a bit.
Is any of this allowed?
See image:
https://ibb.co/rFkXMSB

I don't see why Green box wouldn't be allowed (potentially subject to party wall agreement) but no-one on the street has done it. Yellow may not be allowed since width is larger than 50% of house, but everyone on street has done it, so probably planning permission?
I don't see blue ever being allowed.
Is it possible extending from Garage 6m to partially do blue?

I'd love to hear suggestions on what would be allowed to extend here to make the most of the space.

Thanks!

 

[steveinoz01]

Assuming the black outline of the house is the original unmodified house then yellow and green should be good subject to max depth for rear extensions under PD and height at boundaries and not more than 50% of width of existing house.

Blue one looks like it will be way more than half the width of the house and the depth will be measured from the back of the garage.

You could go for full planning instead of PD if you want to do more than PD allows and there have been little or no modifications to the house in the past.

 

[DevilDamo]

Yellow would need to meet the PD guidelines for side and rear extensions. Green would need to meet the PD guidelines for rear extensions. Blue requires formal Planning.

Your PD guidelines would be those relating to a semi-detached house.