I have a budget dash cam
https://amzn.to/3RZh6iH far about £30 plus a decent sd card
https://amzn.to/48e7rdY 32Gb for about £10. It has worked well but it wont do any recording after the ignition is off.
I do make sure it's working every day by checking the screen to see if the recording icon is on and about once a month I take the card out and check a few files to make sure it's ok.
I did recently come very close to an accident. Some young girl pulled out in front of me from a side road. She didn't edge out but fully pull out so close that I didn't have time to brake, just lucky no one coming towards me as I had to use the right side of the road to avoid her! I could just see the impact flash before me...... Looked back at the footage and boy was it close. I hope that if the accident happened the footage would have proved she pulled out on me.
Not sure how well you could get a reg plate at a distance but for showing who caused an accident I'm sure it would help.
Some insurance companies give a discount for a dashcam.