Favourite International's a liquor importer and distributor, and they supply to a lot of our favourite spots in Colombo (Barefoot, Colombo Courtyard etc). They've also opened up a stand-alone shop in the busiest strip in Negombo, Poruthota Road.
Their inner "cellar" area has a pretty commendable selection of wine and sparkling wine, including a variety of affordable brands like Frescobadi, Nederburg, and Borsao. The selection wasn't vast, but it was thorough, so you should have no difficulty finding a crisp Riesling or a full-bodied Cab if you're craving it. The champagne selection is limited, with just a couple of Besserat options on display (Rs. 9000), which is a little disappointing. But if you're looking for bubbly, the prosecco variety is great, with options like Cave des Rois and Treviso along with some Valdivieso Brut. They're all very affordable at about Rs. 2000 a pop (literally, heh.)
The cellar itself is pretty compact so there's just one member of staff to efficiently explain, recommend, and bill your purchases. When we went, we met someone who was quite helpful, and quickly identified our tastes and budgets and made appropriate suggestions.
The outer area functions as a normal Lankan liquor shop would, with a Government-mandated green licence sign outside and a circus cage ensconcing the cashier and the goodies. You'll get your usual cheaper wines, along with a wide selection of beers (everything from Lion Lager at Rs. 200 to Benediktiner Weissbier at Rs. 760) keeping the usual Negombo tourist crowd in mind. The caged cashier was very helpful, and even convinced my friend we were getting a discount (we weren't, as it turns out, but my tourist friend felt special anyway).
Not much more to say really, but the place is bright, well stocked, and well-priced. The perfect pit stop for a boozy beachy Negombo weekend.