What you want to do is fine. My point only applies if you were to change the returns so that the hot water return joins the other returns other than as the last junction before the boiler.
That’s great I just wasn’t sure if the returns to the radiator had to be the same or similar length/root to the flows to get even flow/heat.
In that case I will leave the returns as they are and will just lift the flows off and put in a new manifold back to a new zone valve off the main flow
Also doing this won’t mess up the last flow from the hot water cylinder
I have also contacted Ariston the makers of my boiler and they have said my boiler has an internal bypass valve fitted so I don’t need to worry about fitting an external one
Cheers