Gary... If you are looking for the linen, pettah is the best place... all the whole sale dealers are there... however better accompany one of your local friends when shopping... If you are luckey enough, some shops are selling batik too... else you will find many shops towards the Kandy... however those on the Kandy road聽 are catering towards the elite and pricing is bit higher than the usual...
If you are in Colombo, laksala and salusala at Jawatta found to be another option (for the batik)
Price tags at Laksala found to be bit higher than the Salusala...
If not visit the Odel at Alexandra Place or the Town Hall
For the linen, it should be the pettah market
