Hi David,
Look you cant change what's gone, history is in the past so don't beat yourself up about that.
What you can do is change the future going forward for you. Now you are a bit older and more mature and you have a possible passion for Engineering, well that's great, focus on that.
Personally i probably wouldn't go back to college to do subjects again for another two years. I appreciate physics and maths are important but equally I think that could demotivate you, two years of the same with peers younger than you.
Yes your subjects were not great choices but you do have 96 UCAS points and you wont be on your own, thousands of students up and down the country get encouraged to do duff subjects simply because the schools want top headline figures rather than what's best for students career futures
NEVER give up on your dreams, you go for what you want. Heck if you have a go and fail at least you tried your best shot. There is nothing worse than not trying.
Anyhow, if i was you i would look at two options:-
The first option, If you want the University experience and a degree in engineering and think you are ready for that and can apply yourself then look at a foundation year rather going back to college:-
https://www.whatuni.com/degree-courses/search?subject=engineering&score=0,96A few options there but a foundation year leading into a degree with placement year i think would be really good, then at least you get some real skills job training alongside your academia.
The other option is to look at going down the apprentice route, sticking with just plain academia is not for everyone and there is nothing to stop you returning to a degree if its still something you want to do later:-
https://www.apprenticeships.gov.uk/apprentices/browse-by-interests/engineering-manufacturing#Anyhow, good luck with what you decide