This comes up as an example of 当社比, in fact the only one. It's pretty useless for that, so I have chopped 当社比 off the index. I can't see how it applies to the sentence anyway.

(ymmv) was the translation of （※当社比） in the original Japanese. I thought it was quite a nice example of 当社比, in the colloquial sense anyway.

See
http://kotonoha.cc/no/70211
for an internet poll on 当社比 usage.

The trouble is that the 当社比 bore no resemblance to the meaning in the dictionary, so a couple of people complained about the link. Can you suggest another meaning, and perhaps a new sentence using it?

Well, we have this:

http://d.hatena.ne.jp/keyword/%C5%F6%BC%D2%C8%E6
1. 広告においては、性能の向上を示す数字の比較対象が自社の従来製品であることを表す言葉。しばしば非常に控えめに表示される。
2. 広告以外においては、殆んどの場合、比較対象が主観に過ぎないことを表す言葉。

So by that the original translation could be put like:

Great Britain is a land of gentlemen and horse riding. (NOTE: just my idea of it)

Personally I thought that ymmv parallels that very nicely (it was somebody else's suggestion). YMMV is also used on a personal basis.

e.g.
http://bigstarlet.posterous.com/
Sorry if you're tired of it, folks. Sometimes, train wrecks fascinate me. YMMV.

The JMdict entry for 当社比 has been extended, and has a second sense: "(2) (col) as I see it; by my estimate". That means the
"（※当社比）" could go back, along with the "ymmv". It would eb good to have a better example.

You might find this example useful.
http://tatoeba.org/eng/sentences/show/2263845

I think グレートブリテン should be changed to イギリス. Whereas "Great Britain" commonly refers to the UK (as in this sentence), グレートブリテン always refers to the island.

We can presume that the English sentence is the original. And in that case, "Great Britain" definitely refers to the country of the United Kingdom. I think グレートブリテン is a mistranslation here.

Not a great sentence pair. It's the only one using グレートブリテン.

Maybe we could add a sentence talking about a geographic feature of Great Britain.

#12400996 The British Isles consist primarily of the islands of Great Britain and Ireland.
#12401008 Scotland makes up much of the mountainous northern part of the island of Great Britain.

#6276895 Which countries make up Great Britain?
#2427868 Great Britain consists of Wales, England, and Scotland.
#54074 Now, I would like you to imagine a map of Great Britain. (has a TC translation, 大ブリテン)
#666046 The new tunnel will link Great Britain and France.
#9797696 The inhuman ideology of racism was widespread in the United States and Great Britain.
#11849985 The islands of Great Britain and Ireland were disputed by a crowd of princes of Saxon or Scottish origin: and, after the loss of Spain, the Christian and Gothic kingdom of Alphonso the Chaste was confined to the narrow range of the Asturian mountains.

Looking forward to Japanese translations of some of those.