I'm using <xsl:template match="..."> but otherwise my code is identical.
Would the use of the <xsl:for-each select="..."> make any difference in
this instance?

You can equivalently do as
<xsl:apply-templates
select="br[local-name(preceding-sibling::node()[1]) = 'br']" />

and the corresponding template definition as
<xsl:template match="...">

Regards,
Mukul