I've been going to this place whenever I get the time (usually to grab takeaway which I'll have the next day) as every meal I've had there has been excellent, but I'm always on my way to Thattukada when I pass it. The restaurant itself is just off High Street North on the same road as The Overdraft (Sibley Grove I believe) with easily visible signage. The actual interior is extremely small with no real seating besides a few stools which were only recently added.
The business is family run with a different relative (or set of relatives) manning the counter each time I've gone. Nothing is prepared to order unfortunately, but the quality of the food in their steam table is extremely impressive. The prices are also shockingly low compared to somewhere like Lihiniya (which I need to get back to ASAP now that his wife is in town) and everything I've eaten at Nadi has been better than equivalent dishes in Cricklewood (though again, I need to give it another shot now that the owner's wife is back.)
So far I've had the maniokka (fried casava) with homemade chili chutney, the banana flower curry, the jackfruit curry, the dal curry, and the lamb curry. Everything has been incredibly good, though the real standouts were the jackfruit and banana flower dishes. The latter seemed to also have dried fish in it (so ask in advance if you're veg) which added a textural change to what was otherwise a mass of banana flower petals. Extremely nutty with a note of dried fish. This is also the first non-Bangladeshi banana flower dish I've ever had. The jackfruit curry was tangy with tender jackfruit and a much thicker "gravy." Very pungent tang with a lot of spice cutting it ever so slightly, but quite addictive. The lamb liver was also one of the better dishes I've had there though it was extremely simple. Relatively large chunks of liver were practically caked with chili and then cooked up with onions, chilies, peppers and scallions. The flavor was much simpler than the above two dishes, but the liver itself was delicious without an overly mineral-y taste. I had it microwaved at home the day after I bought it and it still held its texture and flavor without a strong aftertaste.
All in all I've spent about 15 pounds at this place for all of the above dishes I've tried. It's -really- cheap and the takeaway portions are large enough for a couple of meals. They seem to be doing decent business, but their location and lack of seating means that they could probably use the attention that Chowhound may bring.
The food is distinctly Sri Lankan and the owners are Sinhalese. They also have breakfast in the morning with kattu sambol, string hoppers, etc on offer. Unfortunately they don't have hoppers and given their steam table arrangement I don't even know if the cooking is done on the premises so this might not change.
And this is the part where Dave goes and writes a follow up post ;)