Mobile Catering Insurance for a Burger Wagon

I am trying to start up my own burger wagon business but I have been told I need to get the wagon insured but at this present moment in time I don’t know where I have to go to get my wagon insured

I live in Milton Keynes, Buckinghamshire if you could help me that would be wonderful,
Could I also keep in touch just encase there is anything else I need to know.

Thanking you very much.

Rose.