Your swaybars must be leaking.

 

The fluid is coming back out of the filler bottle cap though? Would a leak in the sway bar cause that?

 

Oh, missed this part. Point is I can not imagine any circumstances for this to happen overnight, as the ACE pump only works (and creates fluid pressure) while the engine is running.

Assuming this, the ACE pump circulates the fluid and is directed by a couple of valve bodies (I'm recalling it from memory here, so this may not be a technically accurate description). If one of the valves is stuck, the fluid pressure will seek the point of least resistance and the filler bottle seems the perfect spot - your ACE system tries to work but the pressure does not go to the swaybars, the fluid gets ejected via the bottle cap.
Perhaps there is some residual pressure in the system after the engine is shut off and this give the impression of the fluid disappearing overnight?

 

Thanks for that, yes the overnight bit could just be happening because that’s when the car has sat still after being filled and road tested.

do you know where the fluid valve blocks are located please?

 

Behind the right front wheel if I remember correctly. Part number LR072419.