Trendy or classic?

I am due to start a winter vacation scheme next week with a large City firm and am worried that I have nothing suitable to wear.

But before splashing out on some new gear I wanted to get people’s thoughts on what sort of clothes would be appropriate. Shall I go for something trendy from Top Shop or Oasis for instance or is it better to opt for a classic suit? In fact, how much attention do law firms pay on what candidates are wearing?