Ooh. Lots of good suggestion from you lot, thanks.

I agree that 'actual' motorway barrier would be over-spec.
Something of that 'style' but smaller and more aesthetic is what I'm
thinking and my client's wish is for something that will last much
longer than the original timber planks, hence his comment about using
metal.

Scaffhold poles or square sectional steel sound ideal. I'll have a
browse through the links you guys supplied and I'll also pop over to
Cannon Steel in Enfield later on to see if they can fabricate something
for me. This is likely to be much cheaper than something "off the
shelf".

Ta
deano.