Well there we are, mission accomplished. I've had to write a cunning 404 error script, so that any hard links to the *.html files that there are on the web will not 404 and actually find the .php file. Maybe there's a cunning setting in Apache to do this...
Unfortuately the script isn't as cunning as it could have been, because I couldn't get the Location: thing to work from custom error pages, the webrowser would try to download the page as a file and now display it - any solutions would be grateful. (it works using meta refeshing now) Oh well it's done.
Look I can do cunning things now :)