I want to install a vertical, fed with an SGC230 at the bottom, but
concerned about minimising chance of a lightning strike on a bare
conductor.

Hi Nick,
There is virtually nothing you can do to prevent a strike hitting your
antenna. But you can attempt to pursuade Mother Nature to send the damaging
electrons somewhere where they won't do damage. Get a Polyphaser or ICE or
other good lightning arrestor made for this purpose and install it with a good
ground under the antenna. Your objective is to divert the strike around your
equipment and into the ground, taking the path that YOU provide for, not the
one that the lightning strike would otherwise select. Your ground must have
the capacity to absorb the electrons which arrive in massive quantities in a
few microseconds, otherwise they will give up on you and find their own path
to ground, often not the way you would prefer.
There is good information on this technique on the polyphaser website,
probably www.polyphaser.com. Most likely you will get about 50 more replies
so be prepared, this is one of the favorite and most often discussed topics on
this newsgroup.

Rick K2XT