Yes the Sky Hub is not great but I'm afraid the HH5 can't be used with Sky as it does not support the MER authentication used by sky.
I'm afraid your only option is to look at purchasing an alternative router, the Asus ones are good.
That's a pain, I was hoping not to have to spend that much!
The WiFi speed drops to <10mbs when I've got more than 1 device doing something, it's absolutely useless. With the HH5 I've got 4-5 things all running at the full 40Mb but for some reason it keeps dropping out every now and then. It didn't do it when on BT so I can only assume it's the way I've got it configured with the Sky Hub, I'll have to have another go at re-configuring tonight.