I think I've resolved this.

I was originally using GUIMiner v.02 which came bundled with cgminer 2.10.

I am now using GUIMiner v.03 which uses cgminer 2.11.3

This solves issues with my Radeon 7950

Found latest here: https://bitcointalk.org/index.php?topic=117221.msg1256502#msg1256502