docbook xsl: prefix for link and xref in (x)html

Hello,
maybe I'm missing the obvious but here's my problem.
I'd like to prefix any internal link (e.g. <link> or <xref>) with a 
fixed string.
E.g. <link linkend="bla"> will result in the following HTML code: <a 
href="/myprefix/ch01.htm">
As far as I came I found out that customization layers won't really 
help, since in case I override/replace a template I can't just "catch" 
the old template's output (in this case href.target or similar) and 
prefix it with something. I would've liked the solution to be upwards 
compatible with future docbook xsl stylesheets.
Any idea? Thanks.
~jm