does apple tv work with SKY GO?

I suspect they are limited to sites with subscribed streams and a handful of others. I'm not disagreeing they exist, or that you didn't intend to imply they were common, but that was how it came across and the reason for me checking you weren't referring to basic AirPlay functions.

Since you've verified you didn't intend to imply it was common, I'm no longer questioning your statement.

I really struggle to understand why they have this restriction. I can already watch Sky Go on my iPad screen; if I just want to watch exactly the same thing on my TV screen instead, because it's a little bit bigger, why is that a problem? The content itself is something I already pay for via my Sky subscription, but the method of streaming it on demand via my iPad is a lot more convenient for me. (I have an old Sky+ set top box which doesn't have access to Anytime+, so I thought Sky Go would be a good way for me to get access to this on-demand content.). Perhaps it's to protect their multiroom subscriptions, which cost an extra tenner a month? But I am actually a multiroom subscriber too, so it still seems odd to me that I'm prevented from pushing the iPad content out to my TV.

The problem is that people will abuse it.

Say you have a friend/relative with the Sky package. They get Sky Go for free. You get their details and then you can watch Sky Go on your PC, tablet or Ipad/phone, etc.

Obvioulsy they don't want someone watching Sky Go on their TV if they aren't paying for it - so they disable Airplay and mirroring.