is it worth me filing a police report?
No. Why would you want to do that?
Who would you report? Yourself? But no crime has been committed according to your explanation in post #1 of what happened. It was an accidental mistake and you had not intended to drive off without paying - "due to stresses and tiredness, I am probably guilty of the offence and feel pretty embarrassed to say the least, as this is something I would never do intentionally".
See andy-foster's advice in Reply #17.
And you have offered to pay for the unpaid petrol both in the Morrisons store and (twice) in the garage.