Hi Paul,
All understood. I have still to get my own antennas moved outside. Permission received from SWMBO but recently starting to get comments like ‘I didn’t realise they were going to be that big’, so I might have to scale my ‘ideals’ back a bit. I’m still deliberating the best option.
Re taking the coax in, you can get some excellent roof vents designed to match into tiled and slated roofs. It should be fairly straightforward to fit one of these (or have one fitted) in place of a slate. It can be pre-drilled to provide fairly discreet coax access while maintaining the integrity of the roof. Ideally run the coax in from the outside, then cut to length and fit the connectors inside afterwards (if you can) to keep the hole sizes to the minimum. Alternatively, depending on construction, you can often manage to feed the cables up through under a slate. If you are using an aerial fitter they will have done it all before.
Regards
Peter