Hi Peter,
I too purchased mine from HK via ebay and used the same supplier as above - "hkyongnuophotoequipment".
When they arrived, a socket on the transmitter was loose (was functioning correctly - just the internal back nut on the socket was loose), so had to return it, - but apart from the short delay arising from using international post, I could not fault them and they kept me fully informed at all stages. The replacement/receivers have been working perfectly now for about a year.
Very pleased with them.
Roy