Wh.ile driving south along the M1 a couple of days ago and around 4pm
there was a solitary bright light in the sky....was this a star and if
so which one or was it a planet?.....

I don't know what or where "the M1" is, but Venus can be incredibly
bright in the early evening at this time of year.

I'm assuming you're talking about the M1 in Johannesburg.  Actually at
4PM in that location Venus would be at your zenith (directly
overhead), so unless you have a sunroof in your car, and were looking
directly up through it, I can assure you that it was not Venus.  There
were no planets in the southern half of the sky at that time, although
Mars was due west, and can be very bright since we are very near that
planet.  If you noticed that it was moving, it is probable that it was
a satellite.

If it was not moving, the brightest object in the south of the sky
there is a star called Rigel Kentaurus, in the constellation Centaurus
with a magnitude of 0.1  Only two stars are brighter (Sirius and
Canopus), and both of those were not visible at your location.  If
you're sure it was in the southern sky and not moving then it must be
Rigel Kentaurus.  That was the brightest object in the Johannesburg
sky at the time, located 35 degrees above the horizon, south of
southwest.

Morpo, it could be the M-1 in the UK. Simonfen, try visiting
http://skyandtelescope.com/observing/skychart/skychart.asp for an
interactive sky chart. Input a location and time/date and you can scan
the sky.

For 20 November 2005 at 4PM at Greenwich England, Venus was a dozen or
so degrees above the horizon around SSW (as Pinkfreud noted). Also,
Mercury might have been glimpsed for a couple of minutes trailing the
sun by a few degrees after the sun dropped below the horizon.

Yes, the M-1 *might* be the one in the UK. Or it *might* be Michigan
State Highway 1. It's the OP's responsibility to make this sort of
thing clear to the readers. If simonfen thinks the M-1 is relevant,
then simonfen should say clearly where it is. Does simonfen think that
everyone on the internet knows where the M-1 is? Does simonfen know
just offhand where U.S.-31 is? It's a very large world.

Greetings,
If you saw a star at about 4 pm, you were certainly in the northern hemisphere.

You could have been seeing the International Space Station.  It is
about the brightest thing in the heavens when it is visible.  It also
has the nice feature that it moves from west to east - a few minutes
to cross the sky - so you know it is not a star.
Here is a a sight that can help you look for its reappearing.

http://www.heavens-above.com/

Good luck, Myoarin

M1 is the UK. Main road out of London going north south.

Yes it was venus.

I am pretty sure it was venus too. It's sometimes so unusually bright
I have mistaken it for an aircraft before whilst in the car.