A creative writing course was probably run by someone working from home. The entire assets of the company might not total more than an elderly PC, an equally elderly printer and a stock of paper and envelopes. If that's the case there will be no money to distribute among the creditors.
If the business was run as a limited company you can find out who the liquidator is by going here:
http://www.companieshouse.gov.uk/info
Enter the company name. Leave the default options of 'alpha index' and 'current/recently dissolved names' unchanged. Click 'Search'. You should see the name of the company, highlighted within a list, with 'in liquidation' alongside it. Click on the number in the left-hand column. Then click on 'Insolvency History'. Then click on the link alongside 'Case type'.
When you know who the liquidator is your son can submit his claim for a refund but I very much doubt that there will be any funds to pay him with.
Chris