Many thanks for all this information, I now understand things a bit better! What I didn't tell you is that the Arduino software has a mode for testing the radio outputs so I can use this to monitor the outputs as I change the mixing, I didn't realise that the steps in the radio pulses equated to the steps in the servo position.
My background is in construction "Bricks & Sticks" so I'm OK with the glueing and installation side of modelling, but not so hot with the electronics.
I'll try things out later today and let you know how I get on.
