Take the train to Braintree station, which is the end of the line. From there you can get a taxi to St Paul's - it's about a five minute drive. Alternatively, you can walk up Railway Street, turn left onto Manor Street, then up Chapel Hill, turning right at the top. It's a 15 minute walk.
Travel down the A120 until you get to Galleys Corner roundabout; take the turning to go up Cressing Road, and you will see St Paul's on your right after about 1km.
There are three roads that lead to St Paul's - from Cressing Road (either up from the Galleys Corner roundabout on the A120, or down from Coggeshall Road, by Tesco Express); turning right at the top of Chapel Hill; or going down Hay Lane from Coggeshall Road. Note that Hay Lane South is not accessible from Hay Lane North by car or motorbike.