What a pain! They don’t have to give you a refund yet, unfortunately. They can offer a new course date for you to take – and only if you can’t make the new date can you request a refund. As you paid on your debit card, unfortunately there’s little payment protection or way to claim that back from your bank (unlike with a credit card provider, who is jointly liable for any purchase over £100).
It is likely they will try to keep hold of all prepaid courses and reschedule them, rather than offer refunds – especially if they’re a new business. If they do go into administration, you’re able to register as a creditor owed money (but you may not get your full money back).
Sorry I don’t have better news for you right now – keep trying with the emails, and phone calls, and maybe see if they have a social media channel that you can try, too. The squeaky wheel gets oiled!