Unless you are looking for a very specific type of music, you will probably be interested in information that gives you a broad overview of what is going on this year. So a good option is to explore the Festival Calendar 2014. As you will see the early events, starting from the current month of March, are all on view, and if you log in you can also be sent regular updates in advance of the main festivals.
Of all UK festivals, the ones with the broadest appeal are probably the Isle of Wight festival, the Reading rock festival and the Glastonbury event. The Isle of Wight is in June this year, starting on the 12th, and the line up includes the Red Hot Chilli Peppers and KIngs of Leon among other famous names.
Glastonbury, which is later in the year is still confirming which artists will perform there, but several names are confirmed already - you can see the latest news about this here.