There was a shop at basement level in Takashimaya that sells top grade Chinese tea. Many varieties and the cost is about what you'll need to pay in China. Not sure if it is still there.
1) Ong Fatt Hong for pu-erh tea, his brother owns tea shop in hongkong, so some good tea comes over from there. at smith street the hdb there lvl 1
2) Wang San Yang Tea merchant, main shop at hong lim complex lvl 1, another outlet at vivo, has decent tky and some wuyi teas
3) Liu Hsiang tea craft at liang court lvl 3, premium chinese teas, huge variety, even has 25 gram packs for people whom want variety and not quantity. highest quality green teas in singapore .
4) chinese tea house.. bugis.. taka basement... decent tea quality.. of various types.. except green teas from them are a little...