They are now introducing Add On packs. https://community.virginmedia.com/t5/Virgin-TV/New-Pick-n-Mix-pack-options/td-p/3980176
But no option to remove channel types, with one exception, which has been there for many years. There is an option in the Settings menus to remove the Adult channel listings from your TV Guide.
These Add On packs seem to be aimed at lower packs adding services rather than the other way around.