The interview with the student support team, I'm assuming is related to the credibility interview. If so, you should receive a link from the university where you're able to book a slot for the interview.
Since you received an email from the Coventry University with your offer letter, you should be able to respond to the same email address.
According to the Gov.Uk web page, the Academic Technology Approval Scheme (ATAS) applies to 'all international students who are subjected to immigration control and intending to study or research at postgraduate level in certain sensitive subjects'. However, if you are a member of the 'EU countries, the European Economic Area (EEA), Australia, Canada, Japan, New Zealand, Singapore, South Korea, Switzerland or the United States of America do not need an ATAS certificate'.