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!