Help please immersion tank on the blink

[Jamfirstest]

Do I need an electrician or a plumber? It's like warm now. I've inherited this property so a bit clueless

Apparently this could either be your thermostat or your heating element. If it's the heating element you will need an electrician to disconnect and then reconnect before the element is replaced. To do this the tank will need to be drained so you would also need a plumber. An electrician should be able to test for you. An electrician would be able to replace your thermostat for you.