It seems that Sling has completely withdrawn support from the UK (there used to be a UK phone number, which did offer help). This is a disgrace, as they are still marketing and selling in the UK - albeit with older models than are available in the USA.
This is also a shame. I've been a fan of Sling for years, and bought a box as soon as it first came to the UK. I use the box from the USA, where I spend a couple of months each year, and it's tremendous. I get everyone excited about it.... but now Sling has deserted us. The company has, I understand , been acquired. The buyers are perhaps like many you often find in the USA, who think that the world doesn't exist outside the US itself--- a real loss for them, especially in Europe, as we are much better intercontinental travellers than Americans.
As you've discovered, the UK website is irritating in the extreme, as you keep being bounced back to the horizontal scrolling adverts. There ARE ways of struggling into the support and community websites by avoiding the uk website altogether, but even then, navigation is difficult. try General questions as a place to start.
In spare moments, I've been trying to make contact with Sling management in the USA. Or maybe if we can get at least a Slingbox UK Community area of the forum setup, we might be able to help ourselves...