I think it depends on your area, different areas are covered by different contacts. Our contact is, (from talking to a few sencos) very good at insuring the children gt the help that they need. Ours have so-far (but dd2 is only preschool) been pretty good. Have suggested Possible schools with speech and language units to us, and have given us a lot of information and verbal assistance about how to go about getting dd2 statemented.
I also think that a lot is down to the SENCO in the actual school. And they vary greatly.
School admissions is fair, and have been very helpful to us. Dd1 changed schools in the area couple of times.