How to contact One Great Eastern
As is stated on the main web page http://www.southminster-branch-line.org.uk/, one positive step is to contact 'one' about your concerns regarding the Southminster Branch Line.
My personal opinion is that comments are best put in writing, but email to customer.services@onerailway.com is better than nothing. Copying the email to your MP is a good idea. I know for sure that company's take much more seriously issued raised by MP's. Telephoning 'one' is likely to be the least effective method of complaining, and not worth the cost of a local rate call.
If like me you prefer to write, then do so at:
One Great Eastern,
Customer Service Centre,
North Station,
Colchester,
Essex,
C01 1XD.
0845 600 7245
Whatever you do, try to keep points that will benefit most users of the line. Don't get too specific about particular times of trains, as a time that is convenient for one person will not be for another. The long delay between trains is far more important than the exact time a train leaves.