I have just bought an electric cooker, and I haven't got anything to connect it to the three pin socket I have at home (I am in the UK). What should I buy and where should I connect the three (live, neutral, earth) wires (see photos )? The earth cable should go under the right-hand screw, but what about the others?
The electric cooker should have an installation manual. Most electric cookers in the UK are not plugged into a normal 13A wall outlet/socket. They are hardwired to a dual-pole cooker switch on a dedicated cooker circuit (e.g. a dedicated 32A circuit).
A typical cooker instructions will say something similar to this example.
The cooker must be connected by a competent person such as one who is a, NICEIC registered contractor to a suitable double-pole control unit with a minimum rating of 32A and a minimum contact clearance of 3mm (applicable to newer properties, older properties where a 30A double pole control unit and a minimum contact clearance of 3mm is acceptable). The double pole control unit should be fitted adjacent to the cooker, in accordance with IEE regulations. The control unit must be within 2 metres of but not directly above the appliance and should be easily accessible in the event of an emergency. The power supply cable should conform to B.S.6004 with a conductor size of 6mm2, minimum. Access to the mains terminals is gained by removing the rear access cover. The mains cable must pass through the cable clamp adjacent to the terminal block. Sufficient cable should be used to allow the cooker to be pulled out for servicing. Ensure that the mains cable is routed away from any brackets affixed to the rear panel and is not trapped to the rear wall when pushing the cooker into position between cabinets
Examples of the required diversity calculations can be found online. For example: https://www.tlc-direct.co.uk/Book/6.5.2.htm
In your photo of your cooker's connectors, the multiple live and neutral connections appear to be each be connected by a copper bus bar. This presumably means that you can attach the supply to any of the screw terminals (brown to an "L", blue to an "N"). Don't use 13A flex or a 13A plug, it'll eventually blow the fuse or catch fire.