I recently read a book on the fall of Napoleon and the Congress of Vienna. In it there is a vignette about Lord Castlereagh, the British Ambassador, sitting in his carriage outside Paris having an improvised lunch of pheasant salami and champagne. This got me wondering, was champagne such a common wine that Castlereagh was able to get hold of a couple of bottles with relative ease? Or is it more likely that Champagne was a the relatively expensive drink that it was today and he was able to obtain it because of the dislocation caused by war?
Wine production in the region of Champagne France dates to the times of the Romans but champagne as we know it (secondary fermentation in bottle to produce bubbles) didnt really take off till the middle of the 19th century. Glass simply wasn't strong enough till then for it to be mass produced and it took an export market such as Brittan to develop a taste for it.
Champagne was produced at probably could be considered an industrial scale by the time period of your query so there would not be any problem finding some almost anywhere in northern Europe or Russia.
Champagne, like diamond, achieved its luxury status through marketing. In the days before Dom Perignon took over the Abbey of Hautvillers, it was just red cloudy wine made from the same grapes grown in Burgundy. He invented specific methods of growing grapes, pressing and blending them to get good clear wines. The secondary fermentation happened naturally and not until the mid-17th century that its occurence was studied and harnessed to give us the champagne close to what we get today.
Anyway, champagne was a common wine back then. The champagne producers were struggling to compete against the burgundy wines. It's not a surprise nor a privilege that Castlereagh got a hold of a bottle.
These days, champagne is still a common wine in France. A good bottle of champagne can be found for around 20 euros while an average bottle of burgundy begins at 20 euros. But I'm bias, of course, being a champenois.
Read Don and Petie Kladstrup book on Champagne history which covers all this. It's a great book. The most memorable description for me was that more blood was spilt on the soil of Champagne than anywhere on earth, yet champagne is the symbol of celebration of new life and new beginnings.