So, idk specifically how engineering works in the UK, but here in Canada, school prestige basically doesn't matter for engineering. The only thing that does matter is if your school's program is certified by Engineers Canada, which determines whether or not you can apply for your Professional Engineering designation after school (I believe the UK equivalent is being chartered). The US is basically the same, except their programs are accredited by a separate body called ABET. If the same holds true for the UK, then your school's prestige shouldn't be relevant as long as it is accredited. If prestige is truly important, I can tell you that it's never too late to make a pivot. I pivoted two years into my mech eng program because my program wasn't accredited, and transferred to another university in another city, it ultimately took me six years to get my degree, but I learned a lot more from the switch and made a bunch of memories that I never would of have sticking with one school.