Do not expect any high end London party in Fabric. But expect some AWESOME raving.
If you are going to Fabric you should know that you are about to enter an underground club and you will not hear any commercial music.
Tech-house, techno, dubstep, D&B is what will enchant your ears down there. People are just partying and will not give a damn about you. I had the feeling that no one judges your level of drunkenness or the state in which you are. And this feels good !
It is better to go with a large group of friends and get lost in one of the 3 rooms (if not all three). You will get back to the surface with the sun shinning, and you will easily find a breakfast spot in order to chill out after an amazing rave.
Incredible atmosphere!