Bringing Sat cables in through roof slates

Hi all - looking for some tips. We've got some sat cables that are currently coming into the house through a drilled hole in the wall. It's far from ideal, and the wall in question is beginning to show signs of damp/mould on the inside. So the cables will be removed from this hole, and the hole sealed up. This leaves me needing to get the cables in through the roof slates, has anyone any ideas/tips on how best to achieve this without creating more problems than I'm solving? If I prise up a tile, do I look for an overlap in the membrane and just feed the cable through? What if I can't find an overlap (I'll be doing this from a kitchen extension, so will have standing access to the bottom two or three rows of tiles only.) The house is your standard Dublin terraced house from the 60's. The attic itself is plasterboarded on the inside, with the plasterboard travelling down quite far to the bottom of the apex, but not all the way. Would greatly appreciate any input/help/tips/advice