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The research reported in this paper describes a Coloured Petri Net (CPN) method for modelling and analysing reliability and efficiency of the dispensing process in English community pharmacies. The results of CPN simulations are used within an optimisation framework, based on an Ant Colony optimisation (ACO) algorithm, in order to find optimal solutions for a range of process parameters, such as the number of dispensers and pharmacists to employ, prescription checking strategy or staff work pattern. Set-ups are evaluated using a multi-objective utility function with three parameters: the number of prescriptions completed, the number of errors, and the average waiting time. In-field data from 4 English pharmacies are used to control the firing of key transitions of the CPN. The results indicate that if a pharmacy has a large budget the optimal setup is likely to contain many staff, of which a majority will be dispensers. Alternatively, if the budget is small, it is likely the optimal team will be small and contain a majority of pharmacists.