The main focus of the SZ community at present is to utilise the redshift–independence of the SZ surface brightness in order to perform blind surveys for galaxy clusters. While other techniques suffer from large intrinsic biases and complex selection effects, SZ surveys will produce almost *mass–limited* catalogues and thus far superior datasets for constraining cosmological models. The dedicated SZ surveys, for example Planck ([@Ade2011]), SPT ([@Stan2009], [@Vanderlinde2010s]), ACT ([@Menanteau2010], [@Marriage2010]) and the SZA [@Muchovej2011] are now generating results. Many more are expected in the near future, e.g. from AMI [@Zwart2008s]. In order to fully exploit the results of these surveys, it will be necessary to improve understanding of both the ‘selection effect’ due to the presence of unsubtracted radio sources, and also the scalings between cluster SZ observables and various physical quantities, especially the cluster mass. Various groups have undertaken similar studies (e.g. [@Benson2004], [@Morandi2007], [@Bonamente2008], [@Huang2010]). To make further advances, reliable observations of large, well–selected samples are required.

The One Centimetre Receiver Array prototype, OCRA-p, is a two–element receiver mounted on the 32-m telescope at the Toruń Centre for Astronomy of the Nicolaus Copernicus University, Poland. OCRA–p proved its SZ capabilities by detecting four well known clusters at high 