Geeze, British biscuits, British chocolate -- you people really need to expand the geographic reach of your tastebuds.

You're so close to Europe where you can get wonderful German, Belgian, Austrian and Swiss chocolates, and those don't even make the list. :tut:
It's been ages since I had Quality Street chocolates, but they always had that cheap chocolate taste that I try to avoid. We get the orange slices here under the Terry's label (they're sold under a bigger brand name label in the States). They edible, but the chocolate is too gritty and the orange is really artificial tasting. I think we got Roses and Celebration here at one time, but to be honest, they weren't memorable brands, and if I ever saw them in the stores today, I'd walk right by them.
As for good chocolate

I found a tiny, wonderful little chocolatier in Vienna on my last visit there. Pure heaven.

I made sure I packed plenty as souvenir gifts for relatives. The chocolates were a big hit, even if I wasn't entirely sure what I was ordering. My German skills are severely lacking when it comes to ordering different flavours of boxed chocolates, and the woman who owned the store had no English whatsoever.
If I had to pick a reliable, internationally known chocolate maker, there's only one obvious and easy choice: Lindt & Sprüngli.
www.lindt.com 
Lindt also bought out Ghiradelli, which was a pretty good U.S. chocolate maker. If you're in the States and looking for a chocolate bar, avoid Hershey's (horrible) and look for Dove (heavenly).
Here, there is only one decent brand of nationally available boxed chocolates: Laura Secord. Sadly however the brand has been sold and resold and is up for sale again, and the quality has slipped with every new owner. Still it's a better product than Black Magic, Pot of Gold, or whatever else is generally available.
I'm not saying I never enjoyed British chocolates -- Yorkie bars were a wonderful discovery when I was a kid and there was another brand of small, flavoured wafer British chocolate bars that I used to love as a kid (I don't remember the name -- Walker maybe? -- and it's been eons since I've seen them for sale) -- but if I'm going to splurge on chocolate, I really do like the good stuff, and that doesn't include Dairy Milk.

--Toronto