mecirt: I've been hitting the problem as well - turned out, I had the https URL bookmarked, and apparently that one no longer works.
http://www.gog.com/ works fine,
https://www.gog.com/ does not (and I -think- it used to, but no guarantees).
That's a different issue, related to a recent-ish change to our infrastructure. Unfortunately a redirect from
http://www.gog.com/ isn't possible, as far as I'm informed.
The "fun" starts in Firefox, which, when given a choice, will always point you to the last used https:// address when trying to enter a site. For your safety, of course. So if you open the browser, type in "gog.com" and hit Enter, it will gloriously redirect you to the now-defunct address. Unless you type in www.gog.com, at least.
Also, our IT guys checked our stats and there was no real impact on our traffic from the UK area. Based on the e-mail responses I've gotten so far, there's no common ground as far as locations and ISPs are concerned. Our investigation will likely show this all resulted from a server issue, or maintenance we were not aware of.