Leadwort is in deed the common name of (some of ) the plumbago family.

 * Plumbago auriculata Lam. is Cape Leadwort and is native to South
Africa.
 * Plumbago zeylanica L. is Wild Leadwort.
 * Ceratostigma plumbaginoides Bunge is known as Blue Leadwort and is
native to China

For a picture of Ceratostigma plumbaginoides Bunge see 
http://www.hcs.ohio-state.edu/ROFM.acgi?_action=GET&_database=PMI4&_fiel
d=HTMLRecord&_recID=37586

Sandwort, on the other hand, can be seen at 
http://hanksville.phast.umass.edu/defs/independent/chas/sndwort.html
Sandwort is the common name for Arenaria which covers a multitude of
sins.
Several Arenaria would appear to be native to the UK, such as Arenaria
serpyllifolia which is Thyme-leaved Sandwort

There is also Moehringia trinervia which is known as Three-nerved
Sandwort

Of course, the new classifications of plants based on their genetics and
not how they look, probably throws all this in the air.

=======

On a related matter, you may be interested in an article culled from the
January 1997 edition of the North Wales Caving Club newsletter (and
before that from the Daily Telegraph).

In the Daily Telegraph of 27/12/96 Nigel Bunyan writes about research
carried out at Oxford Brookes University on the Alpine Pennycress
(Thlapi caerulescens).  

Apparently this plant (which is a protected species) has often led
prospectors to ore fields.  The University has been doing research at
Hafna mine in Llanrwst, where they have discovered that the plant is
capable of absorbing high quantities of both lead and zinc.  The
research suggests that by cultivating and harvesting the plant it might
be possible (eventually) to cleanse polluted sites such as those around
mines.

Regrettably, the short article does not say how deep the plants roots go
and so how effective it would be on spoil heaps.  Neither does it go
into the process for disposal of the harvested plant matter, which is
presumably just as much of a pollutant as the spoil was.

========

Regards,
Adrian

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