Buying Chinese Vegetables in London
plenty of places - really depends where you are. The Chinese supermarkets in Gerrard Street (Chinatown) are your best bet. There are also chinese/vietnamese stores in Brixton, Peckham, Deptford markets if you live South. Also in Hackey (Mare Street). Sure there are plenty more./.
noticed on my visits to the markets this w/e, found pak choi for £1.50 per lb (ok price) at Islington Market and Tatsoi (mild mustard) at Pimlico Farmer's Market (can't remember the price, but would be a lot dearer) but the Chinese s/m will have better choice if you want the other kinds (Kaillan/Chinese Brocolli, Choi Sum - yummy!) Chinatown s/m tend to be overpriced compared to those found in lesser known areas of London, so feel free to shop around.
This year was a terrible year for gardeners (my veg was so bad) but usually Chinese veg. are easy to grow in this country (Mustard Greens and Kaillan have been my past successes, very easy to grow btw.) So try and grow your own next year and you'll save a small fortune!