You could add a common flow and re-use existing as 2 x returns as Tony stated.
This would reverse the flow direction to the ground floor rads which would not be a problem re swept tees but would involve swapping the TrVs on the ground floor to the other side of the rads.
This would reverse the flow direction to the ground floor rads which would not be a problem re swept tees but would involve swapping the TrVs on the ground floor to the other side of the rads.