How about some plain coloured flat shoes (preferably black), but fashionable, so ballet pumps? Then some black trousers, but in a good fit. And then a nice blouse, but something fashionable. If you dont have black shoes, then wear the same colour top as the shoes you choose to wear.....? Maybe. I'm not sure, because it doesn't feel like you should need to go all smart suit-ish, but it is an interview. I have bad judgement when it comes to interview clothing!