Smart meter using DLSM/COSEM

Hello im having a bit of trouble getting this to work using a Microstar C2000 Electric meter.
I have both the C2000 and P2000-T meters and i have a fully working code for the P200-T however the protocol changed in the C2000 which is making this a lot harder.

I am using a RS232 to RS485 modbus module (working perfectly) and Arduino Nano.

I have managed to get the Meter response on the C2000 which is displayed as "/BSM5\2C2000-V21"

to get this i am using the following code:

    Serial.println("Meter type");
    digitalWrite(SSerialTxControl, RS485Transmit);
    byte cmd[] = {0xAF,0x3F,0x21,0x8D,0x0A}; // "/?!\r\n"
    RS485Serial.write (cmd, 5);
    digitalWrite(SSerialTxControl, RS485Receive);
    byte a;
    while (RS485Serial.available() > 0)
     a = & 0x7F; // convert 8N1 to 7E1
     char b = a;

that gets the meter handshake and the meter sends back the response.
The problem i am having issues with is actually sending the OBIS code in the correct format.

Using the P2000-T i sent it like:

  String OBIS = "1-0:0.9.2";
  String sendingData;

  sendingData = "";
  sendingData = char(0x01);
  sendingData += char(0x52);
  sendingData += char(0x31);
  sendingData += char(0x02);

  sendingData += OBIS;

  sendingData += char(0x28);
  sendingData += char(0x29);
  sendingData += char(0x0A);

That use to work perfectly, however not with the C2000.

Has anyone else got a working header format that they know might works ?