[susan53]

Your original idea is correct. Where you are going wrong is in thinking of wine as an uncountable noun. In this sentences it isn't - it's countable.

Rather than saying that nouns are C or UNC, it's more accurate to say that they can be used countably or uncountably. Whether we see something as countable or uncountable depends on our view of the world - do we consider it to be a mass or an individual object. This is often completely idiosyncratic, even within a language - for example English sees rice as a mass, but oats as individual grains - and between languages is often quite different : Italian sees oats as uncountable, like rice - avena.

But even within the language, worldview can change. We normally think of the musical instrument a piano as C - I bought a new piano yesterday. But what if you were writing a book for kids about a family of termites ?
Mummy termite to baby termite : You're hungry? come into the sitting room and have some piano.
Seen with a termite's worldview, piano is a foodstuff, and therefore logically becomes uncountable.

Back to your query... With nouns like wine, cheese etc, there are two ways of looking at them. You can see them as a mass - so if I say I like wine/cheese, I mean all wine/cheese. Or you can see them as individual types of wine/cheese - Bordeaux is a wine / Gorgonzola is a cheese.

So in fact, these words are regularly used both countably and uncountably. And in your example, it's this countable meaning of "a type of" that is being used :

Bordeaux is rather a nice wine. / Gorgonzola is such a nice cheese.

The speaker is expressing the concept Bordeaux is rather a nice type of wine. / Gorgonzola is such a nice type of cheese.


If you choose to see it as mass (ie all Bordeaux/Gorgonzola) then you use the UNC construction :

Bordeaux is rather nice wine. / Gorgonzola is such nice cheese.

As always, grammar gives us the possibility to make meaning distinctions, but leaves it up to us which ones we choose to use.

I have a sneaking feeling that I've said all this before, but can't find the thread. So apologies if I'm repeating myself. It was quicker to write it out again than search back through everything.