1. Through a stockbroker
Most brokers accept certificated shares, but you may need to send the physical certificate to them first.
They will usually digitise (register) the shares in your account before selling.
Examples: Hargreaves Lansdown, AJ Bell, Interactive Brokers, Charles Stanley.
2. Through the company’s registrar
Contact the company’s share registrar (e.g., Equiniti, Link Group).
Ask them to register your shares in electronic form (CREST) or sell them directly if they offer that service.
Once registered, you can sell through any broker.
3. Direct sale (less common)
Some companies allow private sales to other investors, but this is rare and often requires the company’s approval.