I know I posted something along these lines last year, so apologies for the repetition, but I wanted to remind members that there is an alternative coach service to CSSE / Stephensons.
It picks up from B+M in Chelmsford, Danbury and Bicknacre, then goes directly to the 3 Westcliff schools. It has a slightly different timetable which may be more convenient than the alternative. Phillips run it, their details can be found on the web.

A very good point. We were massively put off by the commute from Chelmsford. With a few days to go to school year we uncovered the B+M Bus going from the Army and Navy (ours is actually SBC and does a few Chelmsford pickups earlier). It's a 07:30 pickup from B+M and drops off at 16:15, saving 20-30minutes on both legs of the journey. Current costs are ~£120 per month for 10months. I think a few more Chelmsford parents would consider WHSB if it were not the fact the CSSE website only promotes the consortium buses.