Those workers providing cleaning services for offices and other working environments for 'Essential Workers' are also classed as 'Essential Workers', and so may continue to provide a service. However, when providing services you should ensure that you put in place measures to ensure that social distancing of both your workforce and customers is maintained. If this is not possible then you must not provide the service. You must also ensure adherence to hygiene guidelines. You should only travel to and from your place of work to provide those services.