Sorry I've had to edit this as I was wrong - having talked to the person I'm trying to do this for, we can change the configuration of the RFID reader - so it now has flow control disabled.
I'm still not getting any data from the RFID module 
To test my max3232 I set it up as a softwareserial and used this example code to talk between my serial ports: http://arduino.cc/en/Tutorial/SoftwareSerialExample
This works as expected 
On my max3232 breakout I have:
T1Out -> PIN2 of a male serial port
R2In -> PIN3
GND -> PIN5
Then on the arduino side
T1In -> PIN7
R1Out -> PIN8
(in the softwareserial example I linked to above I've edited the code like this:
SoftwareSerial mySerial(6, 7); // RX, TX