Don't worry, as long as you can say why that w/exp has led you to social work and what you've gained from it, it'll be fine! Life experience counts as well, so anything like peer mentoring at school, being a prefect, anything you can say has taught you skills you think are important to s/w! One girl already on the course at Reading was a manager of Pizza Hut before she came to social work, and (I think) that was the experience she brought to her interview - she'd been involved in team work and dealing with people and customers.