The posts could well be PETERSON MK3 "UNIBLOCK" posts, (patent 011387822008.4 USA).
The posts are made from a mixture of polypropelene/polyethylene making them very weather and UV resistant, also impact resistancy that is equaled by no other.
The bases are manufactured from impact resistant ABS, and feature a spring lock mechanism with a 3 lever inline lock, allowing the keyholder to remove the top section of the post, allowing access to restricted areas.
During the design of these posts, no fewer that 47 patents were applied for, with the US patent office stamping 39 of them within 24 hours. A new record!!.
The ones in the photograph look like the model "C" variant, with a single 22.5mm light reflective band wrapped horizontally 211mm from the top of the bollard.
The actual design of the post is similar to an 1820 model manufactured by Smith Bros, of Islington, London.
Hope this clears things up.
Dean