Short stop-over not leaving Shanghai airport, UK passport

You are obviously covered by 24 hour visa free transit and you do not need any kind of visa. Whether you will need to approach to somebody at the airport depends if you plan to exit the airport or just stay airside, waiting for your onward flight to a third country. If you want to exit the airport, you will approach 24/144 hour visa free transit where you will apply for a temporary entry permit, but if you decide to stay airside, you will just proceed to the gate of your new flight. Your passport will be checked, but not stamped, in order to confirm your identity for your onward flight, of course and to determine if you have a valid visa or you do not need one for your final destination.