Closing down a limited company can be a confusing process, but it's important to make sure you take the correct steps at the right time. If the company is solvent, there are two ways to close it. The first is a members' voluntary liquidation. This requires the passing of a winding-up resolution at a general meeting of shareholders, the appointment of an insolvency practitioner, and the submission of a Declaration of Solvency form to Companies House. This form must be signed by a majority of company directors.
Alternatively, you can opt to voluntarily have the company "struck off" the register. You will have a responsibility to notify all relevant parties and to file an application with Companies House, who will finally close the company.
It is worth noting that although Companies House will also eventually close a company that doesn't have a director, this is not an ideal way to go about closure, since it can involve loss of control of company assets.