The shop that took my deposit for custom furniture has gone into liquidation

It is not automatically gone, but recovery can be limited. A customer who has paid a deposit for goods not delivered is generally an unsecured creditor in the liquidation, and unsecured creditors are paid only after secured and preferential creditors, often receiving only a small share or nothing. Contact the liquidator, whose details are on the Companies Office register, and submit a proof of debt or claim with your invoice and proof of payment. The stronger route is usually your card provider. If you paid by credit or debit card, ask for a chargeback because the goods were not supplied, and act quickly as time limits apply. If any parts of the order were already made and paid for, ask the liquidator whether the goods can be released to you.