The problem you've got is that in order to pick up and drop off, you have to drive in the bus lane albeit for a short distance, so really the PCN would seem to have been lawfully served.
However, wait and see what the others say. As this is Havering, who will not re-offer the discount when rejecting representations, it is a total no-brainer to register an appeal at London Tribunals because the penalty remains the same, and there are no additional costs.