After going through the recruitment process with the HAT Group, I was referred to Shelley Stock Hutter for an interview.
The interview and assessment took up a few hours or so and was overall really relaxed. They're a very relaxed firm.
The interview was with one of the partners of the firm, followed by a short assessment by one of the managers to test your basic maths and problem solving. No prior knowledge of financial services required, although the problems were based around accounting. Even if you don't understand the actual principles of audit/accounts, spotting patterns in the numbers was common sense. The maths part was simply exchange rate conversions.
Typical interview questions such as "Why Accounting?", "Why the change from your degree?" and competency questions. I was also asked to calculate 15^2, so it's good to ensure that you're comfortable with your multiplication. I was allowed to use paper.