Saving a little longer and getting the 430 exII, (£200), will be of great benefit to you in my opinion. It's a great little flash and pound for pound it's a great price. the ETTL alone will improve your portraits no end. And also if you do want to upgrade in the future to say a 580exII you will have a lovely strobist setup with remote ETTL.
By the way ETTL is, evaluative through the lens, a way the body and flash communicate with each other using the available light hitting the sensor to judge automatically how much flash is needed to expose the scene correctly. it's simple and effective.