Tvheadend

I've got a DVB-T2 and DVB-S2 card in the same PC, and I just want the UK Freeview and Freesat services. It's always been a bit of a pain managing both at once in the same place, so it's very handy that tvheadend allows you to add a channel number offset to a bouquet. Still, my EPG got in a mess with hundreds of obsolete channels and ones from Sky (BSkyB) allocated a number of 0. I deleted all of them and did new scans, but again my EPG was spammed with hundreds of BSkyB channels numbered 0. I only had one bouquet enabled - the Freesat one for my region - and only Freesat and Freeview enabled in the EPG grabber. How can I stop it adding all those Sky channels on future rescans?