Can't tell from diagram; the issue, if it applies to your specific brand of column radiator, is not whether the wheelheads and lockshields are on the flow or return.
Consult the manufacturers instructions for your rads; do they specify a flow direction? If so how is this identified ? (e.g.marking on rad, possibly position of bleed screw if this is factory set)
Then from diagram or by feel (flow hotter) you'll know if this is the issue here.
