Main objective : This is a study amendment to an ongoing study to identify whether relatively simple investigations such as the oral glucose tolerance test or changes in fasting glucose and insulin will be able to detect early metabolic changes in patients commencing thiazide & beta-blockers for essential hypertension. We would like to extend the study and investigate whether short term treatment with the alternative diuretic, hydrochlorothiazide, the selective beta blocker nebivolol, and the potassium sparing diuretic amiloride show metabolic changes. The protocol will be the same as previously with additional non invasive hameodynamic measurements.