Amazingly only 2 days after emailing TfL I have had a response. However I am at a loss to understand their explanation and have requested it in plain English. I requested that the 397 be either changed to a double-decker bus or the frequency of the service increased so I could actually get on it.
At present the buses run every half hour. TfL's response is:
"We have looked into this matter and found that it was a scheduling issue. We have therefore decided to shift the school AM and PM journeys to a spot half an hour earlier in the schedule. Our investigations show that this should better match services with demand and significantly reduce crowding, so a larger bus should not be necessary. This change is planned to be implemented from 13 April. "
Am I being dim? I just can't figure out how that changes anything seeing as the service is half hourly anyway. The "new" service is also starting on Easter Monday when the schools are closed! If anyone can translate this explanation let me know. In the meantime I await their response.