I may be a bit biased since I've just moved to Sut...
I may be a bit biased since I've just moved to Sutton from Central London and pretty much all food in London is divine but... Mama Dumplings is alright. It's not "Oh my god that was a disgusting; I'm never coming back" nor was it, "Wow that was incredible; let's eat this once a week". It was just alright. My husband and I got a takeaway from there due to a howling craving for Chinese one night. We've just moved to the area and have no idea where the "good" places are since no one seems to Yelp in Sutton. We'd walked past Mama Dumplings on the HIgh Street multiple times and there were usually people in there (a good sign). I now realize why the place wasn't packed or anything. It's decent food. The BBQ Ribs were the best, although super greasy (which could be a good thing). They were very polite while taking the order; something the people we ordered takeaway from in London were not. The woman acted as though we were already the best of friends!