I finally rang Sky in January. Not because of one big thing, more that the bill had crept past what I was willing to notice every month, and the last "loyalty" offer they gave me expired after six months and quietly went back up. The call itself took twenty-five minutes and most of that was being passed to the retentions team, who are lovely and very good at their job.
If you are thinking about it, two things are worth knowing before you dial.
You are on a rolling contract more often than you think
Mine had ended eighteen months earlier without me realising, so there was no exit fee at all. Check the date you signed before you assume you are tied in. If you are still inside the minimum term, ask what the fee is rather than guessing, because it is sometimes lower than a few more months of the full price.
Have the replacement ready first
This is the mistake I nearly made. I almost cancelled with nothing lined up, which is how people end up crawling back a fortnight later. I spent an evening reading through the practical side of it, and this walkthrough on cancelling Sky and what comes after covered the bits the retention script skips over. Sort the aerial, the box and the broadband question before, not after.
The regulator side is simpler than it looks too. If you are switching broadband away from Sky at the same time, Ofcom now makes the provider do most of the legwork rather than leaving it to you.
Six months on I do not miss the box. I miss precisely none of it, which surprised me more than anything.