That is the bomb.
If anyone else is looking for details, I have included the contents of my "Actions|Run script" here. I use Zsh.
source ~/.zshrc
#echo $HOME
pbpaste | marked | pbcopy
echo "converted"
#end of script
The pbpaste... converts plain text to markup, which is something I do a lot of. So anyone else just needs to put their bit where that line is.
Thanks deanishe