Feedback from massive (OB) stars is thought to have a dramatic impact on star formation in the ISM. Observations of compact HII regions show strong x-ray emission associated with shocks driven by winds, however ultra compact HII (UCHII) regions do not show this emission. We present a new three dimensional radiation magnetohydrodynamics code for modelling the expansion of HII regions and the dynamics of large scale diffuse ionised gas in magnetised star forming regions and the ISM. We investigate the relative contributions of stellar winds and photoionisation on HII regions with the aim of determining which of these processes is driving the expansion of UCHII regions.