Is it appropriate to exit the MCWP platform when working at height?

No, unless a rigorous risk assessment carried out as part of planning the job indicates that this is the safest and most effective means of accessing a particular location, taking into account the availability on site of other more suitable access equipment and the practicability of providing the same within the required timescales for the task to be carried out. This will need to be taken into account during the installation process.