Restricted Airspace (Temporary) – known as RA(T)’s – are notified in advance where possible within the NATS AIS Aeronautical Information Circular Mauve Pages. Here is a link.
RA(T)’s are usually established for specific times and dates to protect an airborne activity, eg an air display. Please read the details.
Each year, a number of pilots are investigated and prosecuted for disrupting or endangering activity protected by a RA(T).