For others that maybe following the thread, you may be interested to know that I found a really simple way to do what i was looking for. The original file was AVI direct from the back of the sky+ ( s-video through a Canopus ADVC 100 ) to my PC, this was then converted to MPEG via TMPG enc.
The way I cut out the adverts was to use TMPG DVD author, this has a nice cut and edit tool in it. the resultant file is VTS video/audio that can either be burnt to DVD or can be played om the PC through something like Power DVD.
Hope this helps others