I've was offered a job there (at Oxford Circus) a month ago, but then I started law school and I knew I wouldn't be able to do it. They interviewed me three times-which I did find a little OTT for a sales assistant job-but apparently they get loads of applications. The first was on the phone, the second was a group interview (I was also asked to bring in one item I thought Topshop represents) and the third a one to one with one of the managers.
Anyway,it really depends on where you are being interviewed, but here is some help-
The group interview is the hardest because you know who you are against. I met all these people that were all dressed really individually and very trendy (almost too trendy). I even met a girl who was going to St Martins. Be confident and yourself, and make sure you speak up when you're sitting round the table, but don't go overboard, because you'll notice the interviewers (all three of them) getting pretty annoyed-when I was in my interview, there was one girl who went overboard with the being friendly with everyone thing, and when another girl noticed they had the same bag, she analysed where they got it from and the different types of leather, blah blah, to death, so one of the female interviewers got really bored, quickly. The girl was basically trying too hard to show everyone how "people friendly" she could be, and everyone knew it.
The part where they ask you to style the mannequin is the fun part. Make sure you listen to instructions carefully. Rush to the clothes rack quickly though, otherwise the best stuff will be gone.
Oh yeah, be at least 15 minutes early! There was a girl who was just a little late, and they wouldn't let her in.
I've got to say i thought it was all overboard for Topshop, but if they feel like it's what they have to do, then I guess they have to do it. My favourite ppl were actualy the interviewers. Don't be freaked out by them, they're actually very nice. I met one of them a few weeks later in the Cafe Nero when I was with my friend, and he asked me if I wanted the job again, which I thought was very sweet.