You can get an ES, but as has been said, they aren't carried out in every test. You're examiner will give you the spiel at the beginnning about having to do 2 maneovres and maybe an ES. I had 6 tests and had to do an ES in 3 out of 6.
It isn't really that hard, but ideally you do want to have a practice before your test so you know what to expect and don't just jump on the brake! (Need to do clutch and brake.) Also, remember to look before moving off though, as Dimez said. Loads of people stop and in their hurry to move off again don't look. You should do left blindspot, left mirror, internal mirror, right mirror, right blindspot!
I got a minor for my emergency stop, but really you just need to run through it in the lesson before your test. An actual emergency stop (when you need to stop) should be pretty instinctive, but just ask your instructor to let you do it a couple of times because you have to get the brakes to kick in in a certain way. My mate failed for doing an emergency rev though, so be careful!
You are probably best checking that with your instructor. I had 2 instructors, the first only ever taught me to check right blind spot. (I got a minor on a test for that.) My second instructor taught both. I think you should really check both. Left can be for cyclists etc, and right for other vehicles. Get your insrtuctor to explain it to you though!
Near the end of mine, I was wondering why the examiner hadn't marked his sheet - maybe I'd unknowingly done a major - so I didn't think to indicate to go back in the test centre until just before I actually turned, getting my only minor, grr!