Exclusive J/psi and Upsilon photoproduction and the low x gluon

We discuss the potential to constrain the small-$x$ PDFs using the exclusive production of heavy vector mesons. The calculation of $J\mathrm{/}\psi$ and $\mathrm{{\rm Y}}$ photoproduction at NLO in collinear factorisation is described. The different behaviour of the NLO corrections for $J\mathrm{/}\psi$ and $\mathrm{{\rm Y}}$ is highlighted and we outline what might be expected from the inclusion of these processes in a PDF fit.