Please have a look at this little application I found:
http://www.tvxb.com/
It generates an XMLTV file and it appears to work for TV1, TV2 and C4. I did not try to pass the file to Media Portal yet, so I cannot confirm the format is compatible, but the author claims it is. However, reading the xml file, there is dates, show names, descriptions, appears to be OK. It remains to be seen if MP will understand all the info contained in there...
Someone who understands how the software interogates the websites might be able to add (fix?) TV3 (it is there but not working as the web page format changed since the creation of the software and it returns only empty entries for TV3) and of course all the other channels. C4 appear to work as well (only show names and times, no descriptions).
All web page creators out there... please help with this! Should be so easy for someone who knows how to "disect" a web-page...
I emailed the author already (Hong Kong) but he checkes the emails for this subject every 4-5 weeks.