  A set of Smoothed Particle Hydrodynamics simulations of the influence of
photoionising radiation and stellar winds on a series of 10$^{4}$M$_{\odot}$
turbulent molecular clouds with initial virial ratios of 0.7, 1.1, 1.5, 1.9 and
2.3 and initial mean densities of 136, 1135 and 9096\,cm$^{-3}$ are presented.
Reductions in star formation efficiency rates are found to be modest, in the
range $30\%-50\%$ and to not vary greatly across the parameter space. In no
case was star formation entirely terminated over the $\approx3$\,Myr duration
of the simulations. The fractions of material unbound by feedback are in the
range $20-60\%$, clouds with the lowest escape velocities being the most
strongly affected.\\ Leakage of ionised gas leads to the HII regions rapidly
becoming underpressured. The destructive effects of ionisation are thus largely
not due to thermally--driven expansion of the HII regions, but to momentum
transfer by photoevaporation of fresh material. Our simulations have similar
global ionisation rates and we show that the effects of feedback upon them can
be adequately modelled as a steady injection of momentum, resembling a
momentum--conserving wind.
