Small angular scale (high multipole order l) studies of cosmic microwave background (CMB) anisotropies require accurate knowledge of the statistical properties of extragalactic sources at cm-mm wavelengths. We have used a 30GHz dual-beam receiver (One Centimetre Receiver Array prototype) on the Torun 32-m telescope to measure the flux densities of 121 sources in Very Small Array fields selected at 15GHz with the Ryle Telescope. We have detected 57 sources above a limiting flux density of 5mJy, of which 31 sources have a flux density greater than 10mJy, which is our effective completeness limit. From these measurements we derive a surface density of sources above 10mJy at 30GHz of 2.2+/-0.4deg^-2^. This is consistent with the surface density obtained by Mason et al. who observed a large sample of sources selected at a much lower frequency (1.4GHz). We have also investigated the dependence of the spectral index distribution on flux density by comparing our results with those for sources above 1Jy selected from the Wilkinson Microwave Anisotropy Probe 22GHz catalogue.