I now have a great environment set up using Flex 3 SDK for compiling and syntax checking/debugging and ASDT for syntax highlighting while using the LuminicBox AS3 stuff for live output logs and traces (thanks to Bachir for the updated link). It's been working so well I thought that others might benefit from this set up. Incidentally I did install the full Flex 3 plug-in for Eclipse first but it wouldn't load any .as files because of a conflict with ASDT I'm sure.. so I uninstalled it and carried on my way with the Flex 3 SDK. So on with the process.
<sep/>flex2ant you have the ability to add the Adobe Flex 2 SDK command line compiler (mxmlc) to your Eclipse installation. By installing flex2ant you add a specific Ant task to the Ant installation that is<sep/>