I was there when my friend had to ring up D:. I don't recall him being interviewed, it was just a case of finding spaces on courses he wanted to do. Just have all your stuff (UCAS number, etc, ready to go).
Also, you don't have to go to uni this year, you could take a break, then apply after doing another qualification. Don't just take anything, in a blind panic.
Have a look on the Uni websites, they will have a section to their current clearing places. All the information, numbers to ring etc. Make sure you have all your stuff to hand.
Every Uni will be different as to how they will do it, for example I applied for a course at Kent, on their website there was an online form to fill out so I filled that out and then about 5 minutes after that a lecturer from that course dealing with clearing applicants rang me up and made me an offer, asked a bit about myself and stuff.
I doubt you'd get interviewed on the phone to be honest.