Dislike first year at current uni, can I switch unis for the rest of my degree?

Hello. I am a first-year aerospace student and attend City Uni, and my experience hasn't been great. Struggled to make friends, etc... The societies that interest me, such as BJJ and Muay Thai, just don't do enough (I'm guessing due to lack of funding). I'm someone who likes to compete and represent the university, but I can't do this at my current university, but QMUL does do this stuff since I see it in their social media pages. A lot of my 6th form friends go to QMUL too, so that's an extra.

Because of this, I would like to move to Queen Mary, for which I did get an offer, but I underperformed in A-levels (BBD (one mark of a C)), so I was unable to join QMUL, so I had to settle for City through clearing. I'm on track to get a first this year and was wondering if I can join QMUL for the rest of my degree. I also want to change courses to Mechanical Engineering (this is not a big deal, I would settle for aerospace if mechanical is not possible). How would I make an application to join QMUL? Through UCAS? Email QMUL Admissions? How much do A-level grades play a role? Is it too late to switch?

Has anyone switched to another uni in 2nd year?

Any info and advice will be appreciated, many thanks.