So basically your word against theirs, with theirs being taken as gospel unless you can prove otherwise?
You have to cast sufficient doubt on the officer's evidence so that the court is not sure it's correct. What you must bear in mind is that the court will consider that the officer has little to gain from committing perjury whereas you have a lot to gain by convincing them he is mistaken. You have the additional problem that despite being asked twice on here what you actually did or did not do, you haven't elaborated on
"I may have looked down and fumble with my phone for a brief moment to turn of a reminder alarm". If you do that in court it won't help you convince the Bench that you did not use the phone.
What incentive does a person have not trying their luck contesting?
The Criminal Justice System is not a game where you "try your luck". Its aim is to convict the guilty and see the innocent acquitted.
are their additional charges or points?
No additional points. Six is the only number that can be imposed for the offence. The court does have the power to order your disqualification for any period they see fit, but this is very unlikely.
But there are considerably increased financial penalties. If convicted you will pay fine of half a week's net income, a "Victim Surcharge" of 40% of that fine and prosecution costs of around £650. If your weekly income if £500 it will cost you £1,000.
Also, what happens to lying officer if you prove you weren't doing what they accuse you of?
If you adopt the approach that the officer is lying you will received short shrift. The best you can suggest is that he was mistaken.