Normally when a limited company goes bust they are placed into the hands of an insolvency practitioner "the receiver" and the stock/assets held by the failed company is sold off to release cash for the preferential creditor/s which are normally their bankers.
Whether or not the stock/assets at Jessops premises have been paid for does not matter and that includes any purchases by customers that were not delivered prior to them ceasing trading. The suppliers who have not been paid would have to join the creditors list. Including customers who have paid for goods not delivered.
After the preferential creditor/s and the insolvency practitioner have taken their cut, if anything is left then the creditors may get a proportion. Probably very unlikely. Unless Canon and Nikon and all the other major suppliers have a legal charge on the Jessops assets they are just a creditor. The stock would NOT be returned to suppliers.