How do I get a dispatcher job in London on network rail please?

I think a lot of dispatcher roles are held by the train operating companies. So you will need to look for the role within the different companies that operate in London at the stations you are interested in. You may want to look at other job roles in stations, and if you specifically want to work for Network Rail then looking at the Network Rail Managed Stations would help, such as Paddington, and Liverpool Street. MTR operate the Elizabeth line and many of the stations on that route. Then it will depend on what job you are applying for as to what experience and skills you need to demonstrate, and aspirations you have for a career. If you are working in and around stations I would say you need to be keen to engage with customers / passengers and deliver a great service.