Worked a bit more towards the podcast. Generating html from php code running locally.
It took nearly 4 hours to debug the http HEAD in php to get the filesizes - the library from http://lwest.free.fr/doc/php/lib/net_http_client-en.html
had a bug in that the HEAD function was also calling a ProcessBody function: since the HEAD did not return a body, the ProcessBody was waiting till the socket timed out or something like that, 150 seconds for each successful call! Also, the Debug variable needed some tweaking.
Later, the xml had a few bugs to iron out - <itunes:category> had to be one of the pre-defined ones, guid couldn't be repeated, publish date was not RFC 822 compliant, had to do string replace for space characters to %20...