Not sure if it's trying to load some kind of external content that's not allowed when captive portaled or it's rate limited but Trying to load the Sky Wifi portal was terribly slow earlier today.

It litreally took me nearly 5 minutes to load the page and add the Laptop I'm using at the moment as one of my 6 devices.

Once i'd added the device I was able to access the internet and the page sped up drastically so it looks like something funny going on when the device is in the pre-auth state.

I'm getting a speed test of 7Mbit/s down 1Mbit/s so I suspect it's on the end of an ADSL line, then again the first thing I did after authenticating was fire up an SSL VPN as I'm paranoid like that.