As Kevin has already indicated, Lambert / Viscount made a (nasty) campagnolo clone post in the 1970's, the clamp arrangement didn't seem anything like as robust as campag - and certainly was not as well finished.
Apart from that I think the the answer is no, though Birmalux did of course manufacture plain alloy posts that needed the separate steel serrated seat clamp - no clubman would be seen dead with those though...
Most of us just used Campagnolo - later Milremo was available from Ron Kitching for the more inpecunious as I recall.
Ian Briggs
Luton, Bedfordshire, UK.