To continue :
Turkey, Portugal, Morocco are all good places to buy cotton based clothing from, but the essential ingredient is to work with a company/agent that fully understands your requirements and can deliver the end result.
China, Vietnam, Thailand and new kid on the block, Myanmar are the best of the bunch in Asia.
If the design is your focal point, just buy plain t shirts and use a local printer (Leicester is full of them) to print your work.
Start small, grow organically.