In the UK, the Ozone Regulations came into force in 2000 and banned the use of ozone depleting HCFC refrigerants such as R22 in new systems. The Regulation banned the use of R22 as a "top-up" fluid for maintenance between 2010 (for virgin fluid) and 2015 (for recycled fluid). This means that equipment that uses R22 can still operate, as long as it does not leak. Although R22 is now banned, units that use the refrigerant can still be serviced and maintained.
The thermocouple is a copper rod that the pilot flame heats-up. When it gets hot enough, the thermocouple signals that there is enough heat to burn the gas fuel being released into the appliance—and so it allows the gas to be released to the burners. In some cases where the pilot light won’t stay lit, the thermocouple needs to be adjusted or replaced. This is generally a job for a professional.