Help! cant open either door on my KA - locks broke?

hiya, i have a ford ka with central locking and about 6 months ago the drivers side lock stopped working, the key goes in, and turns, sometimes makes a crunching sounds, but doesnt unlock the door. Now the passenger door has done the same thing! i can lock the doors from the outside with the key, but cannot open them!? strange....... any ideas?? its like when you put the key in it is just turning almost freely and doesnt unlock the door, and i feel if i turn it any more it will snap in the lock! please help as we have to keep climbing through the boot to get in!!!!!!!!!

how much do you rekon it will cost to get fixed? thankyou!