Recommended lenses for Nikon D7000

Hi all,

In July I upgraded from a D3100 to a D7000 + 18-105mm kit lens and while I love it, I feel like i need to fill in the gap in my camera bag and get another lens.

I also have a 35mm F1.8G which i tend to shoot with 90% of the time.

I'd just like to know what other lenses you would recommend or consider "essential"?

I'm particularly interested in wide angles.

My budget is roughly £350-400.

Does anyone own the tokina 11-16mm ATX Pro and if so, how does it perform?

Thanks in advance!