Hi Simon,

Thanks for reaching out to us. This would be possible if you have two services assigned to one employee. In that case, once a customer chooses the timeslot for service 1, the same timeslots won't be visible for service 2, since the employee is already working on service. In other cases, where you have two employees assigned and configured, this works separately, and your customers will be able to book the same timeslot since it has been assigned to another employee. 

I hope it helps.