Timpdon have given me a long and helpful reply regarding the query "Can you offer Tx and Rx combinations that will allow multiple servos to be controlled in a proportional manner?"
The GRX2 receiver controller has the fgollowing outputs, designed primarily for the control of live steam locos.
1 x fully analogue uni-directional regulator channel - Servo PWM, controlled by speed knob - servo max/min positions user calibrated.
1 x reverser channel - Servo PWM, controlled by reverser switch. This is a 3 position servo, forward - stop - reverse, with servo positions user calibrated and controlled rotation rate.
1 x auxiliary channel - Servo PWM, controlled by Aux 1 switch [ nominally for steam whistle or drain cocks]. This is a two position servo, on - off, with servo positions user calibrated and controlled rotation rate.
1 x serial data channel containing information on all switch settings. This can be used with a GAC1 controller to provide 5 switched outputs - 2 x auto forward/reverse lights, and 3 x uncommitted outputs controlled by Aux 2 to Aux 4 switches.
If you need multiple fully analogue controlled servos, then I can not offer you any suitable equipment.
For flexibility of modelling live diesel in the future this is not quite what I want, but I've repeated it here as it might help some people.
Regards, Tim