You're looking at this from the wrong angle.
You're saying that because the roads were in good nick, you should be able to go above 50. It's not your place to say that. There are plenty of roads that can sustain travel at very high speeds.
The court will see that the relevant authorities have decided that 50 is enough and you did 106.
There's no extenuating circumstances.
Unfortunately the way the law is, there's no contesting the vast majority of speed tickets.
I've heard of people who argued with scientific facts that they couldn't possibly be doing the speeds stated on the speed guns/cameras. They still lost.
You were doing 106 by an 'infallible device'. There's no way around it.
T.