If it's a UK Index registered company AND the shares are clearly in your name only , then I think you have 2 options
a) Find the registrar company for your Company shares. Ring them up , helpline, ask them how do I convert my physical paper share certificate into cash value. They will likely send you couple of forms , fill them in and send them back with your certificate. It's likely they will only process this on a set day each week, say Wednesday 2pm and that's the price you will get for each share. After a couple of weeks after the sale they will send you the cheque in the post , minus manual processing fees.
b) This method is where you have control. Join a UK online share platform , say Iweb, as this is a one time hit you don't need a platform with bells n whistles Iweb is simple £5 per transaction
Once you have joined either ring them up and ask for the forms to transfer your certifcate into electronic form and attach it to your account. Fill them in , send them back with the cert, if all Ok you will see you shares listed in your online account in a couple of weeks. Now the selling is down to You and its just a case of pressing a button and doing a confirmation. So here you can spend weeks watching the shrae price if you wish , or you could just sell as soon as possible. Anyway , once you've done that the value minus the transaction costs will go into your cash account area on the platform. Then you can go there and do a withdrawal to your registered bank account.
