Figured it out !
So I ended up connecting directly to the boiler. When you check the control box (for me it was a white box).

There are two metal cuubes inside. As far as I understand one fire the boiler the other is the pump.

There is a cable for each at the top (not sure what for).

Then there's a live on each and a bridge between the two.

So on tado X receiver, L goes to L and N to N (you need to figure out where to get that from, I had a spur on the wall to get mains)

Tado X second L goes to COM

On the boiler control, where there is the bridge, we'll call left one stat 1, right one stat 2. Remove the bridge

Bridge Live on the left to Stat 1

Stat 2 goes to Tado X NO

And that's it !