I may be an outlier, but I do my clothes shopping online. Let me tell you how they have overcome the problems you have mentioned.

Most online clothes shops I've seen have a really good return policy and free postage. They encourage you to order more then you need, and as well different sizes. So you effectively get sent a whole bunch of stuff to try. You try it on, keep what you like and send the rest back for a refund. It's even better when you're ordering online from shops that have a physical presence as you can just take it back to the store and get a refund instantly.