Roundabout collision: Who is at fault?

Hello,

I am new on this forum and I have done a lot of research on this question as they are several threads but I am still not sure.

http://i1299.photobucket.com/albums/...pslhgtyevx.png

I have approached the above roundabout.

http://i1299.photobucket.com/albums/...pspzqv9vcp.png

Using the "12 O'clock" rule I have used the left hand lane as I am going straight ahead or the 2nd exit.

http://i1299.photobucket.com/albums/...psinfzmxg7.png

As above the round about has 2 lanes. I have made sure the roundabout is clear the proceeded to turn left into the the left lane.
I have not used any indicators

http://i1299.photobucket.com/albums/...ps9ykp0dlp.png

As I have approached the above exit a car has appeared suddenly in the right lane turning into the 1st exit, this has caused a collision.

http://i1299.photobucket.com/albums/...pst8owq5tb.***

This has damaged the off-side side panel and headlight of my car. see above

http://i1299.photobucket.com/albums/...pskl47wtwf.***

The other car has a dent a on the near-side rear panel. see above

There is no signage to indicate which is the correct lane to use.

I am also under the impression that when exiting a roundabout unless any road signage indicates otherwise you have to use the left lane.