Cex was one of the exchange I do trade through in 2017 and I never have problems with them and their customer services has been supportive. However, you cannot compared bitrex, poloniex or bitstamp with Cex and the foregoing exchange are far better than Cex trading platform. If you really want to trade and have peace of mind, I seriously think that poloniex or bitrex are the best but that do not mean that Cex is not good and this op's issue of sending to a wrong wallet is actually a peculiar one and it is hard to find out that Cex do not want to help.