I can't find any square or rectangular plastic extrusions in Europe anywhere. The fence posts nowadays seem to have a slot to accept the railings. I have tried the conservatory websites, DIY centres, PVC window companies, industrial plumbers supply, and every google permutation I can think of. Ideal would be rectangular box section in 1250x1500 (5x6) or anything close really. 6x6, 5x5 - ABS or PVC. Does anyone know where I should be looking?
This 'may' help... Some of the gate post types only have notches at the ends, if you saw off 6" or so you will have a blank post. They're usualy about 6' long so you'd end up with approx 5' of square post.