Accused of driving 25 miles over the speed limit

Looking for advice. I was pulled over last night while driving at 70mph on an A road. The officer advised me that he clocked me doing 96mph with his gun, which he proceeded to show me.

The trouble is I was traveling at 70 mph with my speed limiter on, similar to cruise control. Both my car and Google maps showed 70 at them time and I am 100% confident in this fact, unfortunately with little to no proof.

I'm a 'new' driver having only passed 15 months ago, I never speed and I never drive without my speed limiter on.

I was informed that I will receive a court summons and will have the option to plead not guilty, however I'm just not confident that I have any way of proving my innocence.

Looking for advice on what sort of punishment I am to expect? I understand that 6 points would be my license revoked. I have 0 run ins with the police, and no past records of speeding.