I buy a bottle of wine from a supermaket - can you tell where it's come from? Many wines are often sold under different brand names, or sold with a very generic label (Merlot - France).

Of course these wines will all have come from a chateau/co-operative/blender somewhere, I was wondering if there was anything on the label that would identify these wines further, or if it is pot luck.
Depends on the country, but companies can make it very hard to find where the wine is made and where the grapes are grown. Looking at large supermarket brands, sometimes all that is necessary is listing country of origin and a vague address on the back (and other things like alcohol % and size of bottle). They don't even need to put the types of grapes on if they don't want too. So, to your questions, if you can't find anything on the label about the manufacturer of the wine, it will be very difficult to track it down if they don't want. That's the price you are paying, a super low price without a lot of questions asked.