I don't want to do it as a stub stack (which was the original plan) as I've now got foul waste from a first floor bath and a downstairs shower and basin which will need to run to a vertical stack. There are currently two other toilets towards the back of the house but these already have their own vertical stack which is the other side of a doorway so that stack can't be used to take branch pipes from any of these sanitary appliances.
My plan is to put a new vertical stack in roughly where the bottle trap is in the left of the first picture ( this will be removed and blanked)
Then would take a long rest bend at the foot of the stack and join in at the Y piece where the short vertical stub is currently connected about four feet away. It's a single pipe drainage system and drains out towards the road at the top of the picture.
I was going to fit a soil elbow with access cap where the wc waste first exits the wall and also fit an access pipe on the new vertical stack just above the branch for the new wc.
Reading the relevant government approved document it simply states there has to be rodding access but doesn't go into specifics . any idea if the two access points mentioned will suffice in this example? Or do I need an inspection chamber? Aware that you don't need one for a stub stack, only an access cap as I remember?