I'd recommend the Lazer XS2 clip-on headset - rather than the usual large,
clumsy earpiece,  the main unit clips on shirt/lapel leaving only a
lightweight earpiece and hanging mike on a short lead in the style of many
fixed headsets - gives the best of both worlds. It's been the easiest to
pair and find automatically with my Motorola V3, gives full Voice Dialling
functionality and allows easy volume adjustment, since the controls are on
the lapel mount where you can see them, not stuck by your lughole.  Clip-on
unit also incorporates a neat magnetic earpiece parking facility. Also comes
with a selection of interchangeable matching colour panels and ear covers. I
am told by those I call that  the repro their end is exceptionally good, one
wouldn't believe I was driving my car at the time I called since there was
no background noise at all. Available from larger Tesco's, about 35 squids.

I am perfectly happy with my Motorola HS820, and best of all they are
pretty inexpensive. I got mine on Ebay for $35

The only complaint that I have is the blue LED flashes slowly on/off
while its turn on. If you are driving down a dark road (at night of
course) this LED is so bright it lights up the inside of your car, and
the reflections on the windows can be annoying. I have seen photos by
some users where they cover part of the LED with black tape to stop
this from happening. I am planning on using black nail polish, once I
get around to it.