G7TMG wrote:

So the ARRL say it should be a prefix and the FCC say a suffix??? sounds
like these guys need to talk to each other...

The way I heard it: If you are operating under CEPT rules, it is
a prefix. If you have been issued a permit ("guest licence") by
FCC (as it was apparently required some years ago and still is
for countries who don't apply the CEPT recommendation), it is a
suffix. So, for a British visitor to the USA it is now a prefix.

As operation under CEPT rules implies more or less that one
is operating from a temporary location, several countries do
not require any more to use the /p or /m suffix (although they
can still be used and may be helpful in some instances). Check
also http://www.ero.dk/ for an up-to-date version of the rules.

73, Jan-Martin