Need to do an annual boiler and water cylinder service (pressurised unvented cylinder). Forgot what kind of special category plumber needed for that, as I correctly remember not any plumber could do it.

What is the going rate for such a service, I’m in Northamptonshire. Just wanted to make sure I don’t fall into Cowboys hands.

not sure of costs but the plumber/heating engineer needs to have his ‘unvented’ ticket.