I've been with VM for years and was paying for landline (which I do use, mainly because it is then free to ring VM support and free weekend calls etc.), broadband, and a mix tv package.
I told them I wasnt going to renew as the new "box" they sent me is absolute rubbish. Or rather is less sophisticated than a freeview box I recently got. They get trying to imply it was because I was too stupid? old? female? to understand it, so I said if that was how they were going to treat me I was leaving them.
To cut a long story short, technically I left, got a call from a company that seemed a bit dodgy, checked its number on google and saw it was legit. So I rang them back (they were astonished) and ended up with a contract that was half my previous one.
The box itself (a 360) is just so badly designed its hard to believe they went with it but you can record, pause etc., and have access to a catch up service (free) and on demand (ie like hiring a video for the evening).
I dont miss Sky Atlantic as I have never had it but seem from an article that you can subscribe via VM to Now TV which would include Sky Atlantic, so that woud be an additional monthly subscription to which ever VM package.
So whether you stay with Sky or move to VM definitely challenge the cost of whichever package they offer.
Who knows what you might end up paying.
(This is the article which gives comparisons of different providers packages and costs https://www.choose.co.uk/tv/guide/watch-sky-atlantic/# )