Hi
I have a case of Château Margauxc 1996 in London City Bond.
I want an advise what to do , either to keep it or sell it and if sell it, what is the best price and where I can get it.
Thank you.

Nice one.
1996 rates at 87%, good, but not great.

Now it really depends on what you want to do.
To be anywhere near drinkable this needs another 15 years at least.
As to value well depends on where you sell it.
Honestly it won't of gain much value as yet as it wasn't a great vintage.

As to where to sell it, well Sotherby's holds regular wine auctions.
Sotheby's - Welcome

Here's some ideas of current prices: 1996 Margaux Bordeaux France : Wine-Searcher.com