How do I take out door key barrel on my Seat Ibiza?

My Seat Ibiza is a 2000 sdi. Afew weeks ago I tried to unlock the drivers door, but the barrel just keeps turning round all the way to the right or left. Then the passenger door lock is not unlcking either. do I need new barrels and key or is it something behind the door panel I can do, Ihave to lean in through the boot and open it from the inside . so need sorting asap. any ideas?