You can usually log into those confirmation things with your UCAS number, the only other number you get is a Student ID which you will use all the way through uni, this will usually start 2000something. When you get your exam results etc at uni, they post them on the board next to a number rather than a name, so people can't see your name next to your results. If you want to know your Student ID now, you can just ring up the uni, if you tell them your UCAS no and date of birth, ask if they can tell you your Student ID, they will be able to give it you, just in case you need it (probably won't).