Don't panic...I can understand that the whole process can be a little more daunting when you will be moving back to England...even if you were born here.
From what you've said, and i've looked at Hot topic (Cheers, i love looking at shops like that) it seems to me you want to something creative as a degree course, now I don't know what is available but maybe some kind of generic design course where you choose your own modules?? I.e. you do what they tell you in first year then in 2nd and 3rd you are given more scope to specialise?? Like one that you can do a bit of clothing design (which could help you with the kind of shop you want to open), graphics (which would help you with video projects) etc etc.... or an art course where you can specialise in design? Like I said i'm not sure whats out there.
As for future career prospects I have been at uni for 2 years, about to enter the 2nd year of my 2nd course, and I still don't know what I want to do with it at the end. Yes as I have recently found out through friends...if you don't choose the right degree it can be so hard for you to find a job in the end...but don't lumber yourself with something you don't want to do...please don't.
Gap year, earning money is a great idea as I know all too well money can be one of the main things that brings you down in your university life.... so having extra money but also being careful with what you do have, is a good idea. And like you said taking a year out to earn the money will show self-discipline, not only on future job applications but also in your university applications..
The best advice I can give you is try and go at your own pace, don't panic...just make sure you meet your deadlines, the last thing you want to do is panic and make the wrong hasty decisons.
Good luck x