I`ve a version of Ubuntu and no idea if this is similar to your version of linux but when I boot up I get the log in screen and in the bottom left corner is an options button. You can alter the language settings there. If you boot into my version of linux there is a menu bar at the top. Choose System>Administration>Language Options and change from there.
the update server may be either overloaded or down. Apparently, there are others having the same problem.
Keep in mind, many thousands of these machines were probably sold over Christmas and I suspect, many people are trying to access the server(s) simultaneously.
It seems an update may cure your problem, so I'd tend to leave it a while until things have cooled down and try again.
Frankly, it's disappointing Acer have shipped machines with these bugs. Keyboard layouts have been well addressed in Linux for at least the past five years, so there's really no excuse for this sloppiness.
I haven't yet seen one of these machines "in the wild", but if you take a gentle look around, normally there is a "system" section, where you may be able to manually reset the keyboard to the UK. Whether that will solve it totally for you remains to be seen. Somehow, I think the update will prove to be essential.