In message , Arthur Figgis
] writes
There are probably dozens of markers up and down the country. I saw a
milepost-style meridian plaque in East Grinstead the other day, and at
the other end there is one near Ottringham in East Yorkshire. There is
a marker in Cleethropes, and I believe Louth.

There's a Millennium Meridian marker on the A10 Melbourn bypass:

http://greenwichbook.com/line/os-maps.htm is helpful.
--
Roland Perry