Not sure what course you want to study, or which University of London college offers it? Use the course search facility on the University of London website to help.
You can search by subject and the type of qualification and the results will show you every UoL college that offers a course in that subject.
Take some time to do your research before you come the Undergraduate Fair so you know which colleges you want to go and talk to.
There is free wifi in Senate House so on the day you can also use your mobile device to look at the course search facility if you need to.