"increasingly chronic fatigue and general bad temper" can definitely be symptoms of a thyroid problem. That described me, my sister, and my old college roommate whilst we were hypothyroid.
Have you had a full thyroid panel run recently including anti-thyroid antibodies?
Some people can be symptomatic even with TSH in range, especially with anti-thyroid antibodies. The current "normal" TSH range is under debate and may be narrowed in the future, since most people without a thyroid problem have a TSH between 1-2 mIU/L. Lab reference ranges may have been skewed by the inclusion of people with mild thyroid disfunction in the sample population.