On the Series 1 TiVos, it was possible to filter out channels supplied to you - those channels wouldn't be displayed in the EPG, or show up in Wishlist searches. That functionality has been removed from Virgin's TiVo, due to commercial agreements with UK channel providers.
This means that creating a Wishlist to search for say, 'football' would return results from various radio channels like BBC Radio Five - if you set that Wishlist to automatically record content, then all football content would be recorded from the radio channels - regardless of if you wanted to record football from the radio channels or not.
Likewise, a category Wishlist to locate Sci-Fi programmes would return content Sci-Fi related content from kids channels like CBBC (and potentially auto-record that content too), regardless of if you ever watched that channel.
However, there is hope that Virgin will come to their senses and at least allow us to restrict Wishlist searches to the 'favourites' channels defined by the users. Virgin Staff Member and TiVo Community Forum poster Digital Fanatic has confirmed that:
It would be a good idea to implement [the Favourites channels filter into] the WishList search. This has already been fed back to VM.There also appears to be issues with specifying negative keywords when used with categories, as noticed by TiVo Community Forum poster mikerr in the same discussion thread.
Lets hope Virgin roll-out out the Wishlist fixes for these issues soon.