Blimey, thats a big question.
Do you still have some of that CNDP...they vary in styles enormously. What was the name of the producer, what was the vintage?
The BIG heads-up you had was keeping it for a couple of years, probably allowed it to develop and mature. Most wine is drunk within a couple of hours of purchase, and in many cases too young.
For me, France is where its at for 'serious' wine.
Start or should I say, continue with the classics. The Rhone still remains fantastic value despite producing some of Frances finest wines. In a similar style try some good Languedoc wines....Hegarty, Borie de Maurel, Domaine de Clavel and l'Hortus spring to mind.
The South West produce some crackers too...and not expensive..Madiran, St. Mont, Buzet, PÃ©charmant.
Try some Bordeaux, but budget for at least Â£10 a bottle. 2005 Barreyres (stunning value), Chalet de Pauillac, Brillette from Moulis and many more.
Needless to say, you are unlikely to find these in a supermarket or places like Threshers, Wine Rack. They are just interested in margin and volume.
Go to Oddbins, Nicolas, Majestics and Waitrose or your local merchant.
Hope that helps for starters.......phew..I need a drink!