Typically you will be offered a package of assistive technology, a mentor and a study skills advisor. The mentoring can be more focused around time management, planning and prioritising workload but can also be someone to talk to about any worries you have and to discuss strategies to manage any problems. Study Skills will focus on your academic work, hwo to study at undergraduate level, making sure you address the question, use correct referencing etc.
A diagnosis of anxiety wouldn't get you any additional support from DSA but should mean your allocated mentor has qualifications in Mental Health so can provide more support in that area. If you do get a diagnosis you will need your GP to complete a medical evidence form to submit this to DSA, your GP will charge for this, probably around £40.