Free Traffic Legal Advice

Hi, I was caught twice in one day doing exactly 35mph in a 30.zone, I genuinely thought it was a 40, my mistake I was picking and dropping my brother off after we attended my nieces graduation. The offences was on 24th July 25. I received notification on 22nd August for Sp30 3 points and £100 fine for each one and I paid for both on 4th September 2025. I filled in the back of both forms and sent them off in the same envelope. I didn't send them recorded just posted it off. Now today 24th January 2026 I've received a refund of both fines, £100 each, directly back to my debit card, nothing else, no letter, email or text. I'm totally confused and obviously I've gone down the rabbit hole on Google and it seems the most likely reason is because I didn't send my driving licence but I'm sure the form didn't ask for it, just my driving licence details. Obviously I don't have anything to refer back to as I presumed it dealt with. Any advice would be greatly appreciated as I'm literally out of my mind with worry right now.
Thank you for taking the time to read this.