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I got a ticket in July 2023 for doing 25mph in the 20 zone about half a mile from my home on the A23 (I've lived here six years and the 20mhp zone (it was introduction in the last couple of years). I did the driver awareness course. 



I just got another (a mile further down the road for travelling at 25mph). I realised that (and I don't think this is any defence) Google maps, which I used to drive everywhere, directed that it was 30mph. It is odd that it's a 20mph because it's a wide busy two lane road with no schools etc. 



I need to reply to the NIP soon. Can I avoid points?



Thank you for any advice

Google maps, which I used to drive everywhere

If I did that I'd be walking within 6 months as it's far from reliable.
Watch out for signs and only use Google as a backup!

Use Waze sat nav app instead its much more uptodate (despite google owning Waze)
Change the default setting in it to
1. Display speedometer
2. Display the speed limit at all times - rather than only when you are exceeding it
3. Warn at the exact limit (rather than some mph above the limit).

And make sure you still look out of the window. The above is not reliable, especially for variable and temporary speed limits (and is not 100% reliable for fixed limits either).

I really don't want to be that guy, but from the image you have posted there clearly is a large 20mph sign on the road.
I understand that its very easy to become reliant upon Sat Navs and such systems but they are no replacement for observational skills.