Yeah - we e-mailed them in the end and they said it's fish-based. Problem is, my veggie friend asked whilst she was in the shop and they told her it was veggie. She took one taste when back in the office and voiced her concerns.
She's complained that she was mis-informed in the shop, and they're sending her some vouchers by way of apology. Luckily, she has sharp tastebuds and didn't go further than that first sip.