Probably worth exploring postural therapies after getting some improvement from physical ones first. Stress is often a contributory factor with RSI injuries. Learning relaxation and meditation techniques is a good way to unwind. Relaxation can also help to reduce pain. Tapes which guide you through such techniques are available at Health Food Shops.
Yoga classes are also good ways to learn posture, relaxation, and physical stretching exercises.
Of course, taking exercise is beneficial regardless of having RSI or not. The habit of doing some form of exercise every day, even if it is only a brisk walk, can bring about substantial benefits. Before trying out any exercise programme you should definitely seek advice from a physiotherapist or doctor as many activities may not be suitable for your own circumstances. Most sufferers usually find that their pain decreases when they gain increased flexibility. This includes treatments like acupuncture and healing.