Well the dll isn't there yet, it's not been installed. It's still in the blib/arch/auto/Gtk2 directory in the build directory. Renaming it as per directed didn't help... wait no it set of a dmake clean and deleted everything. Grr. Trying again.
Righty the error is now The procedure entry point cairo_object_from_sv could not be located in the dynamic link library (null). :(
...I am also beginning to suspect that there is another Config.pm file that I need modification as per the config script I use to set up Strawberry Perl.