  At very high energies (VHE), the emission of $\gamma$ rays is dominated by
discrete sources. Due to the limited resolution and sensitivity of
current-generation instruments, only a small fraction of the total Galactic
population of VHE $\gamma$-ray sources has been detected significantly. The
larger part of the population can be expected to contribute as a diffuse signal
alongside emission originating from propagating cosmic rays. Without
quantifying the source population, it is not possible to disentangle these two
components. Based on the H.E.S.S. Galactic plane survey, a numerical approach
has been taken to develop a model of the population of Galactic VHE
$\gamma$-ray sources, which is shown to account accurately for the
observational bias. We present estimates of the absolute number of sources in
the Galactic Plane and their contribution to the total VHE $\gamma$-ray
emission for five different spatial source distributions. Prospects for CTA and
its ability to constrain the model are discussed. Finally, first results of an
extension of our modelling approach using machine learning to extract more
information from the available data set are presented.
