The short answer
These titles describe different legal roles
“Bailiff” remains widely used, but the legislation normally uses “enforcement agent”. A High Court Enforcement Officer, a certificated enforcement agent and a County Court bailiff are not interchangeable.
High Court Enforcement Officers hold authority for the execution of High Court writs. In practice, a certificated enforcement agent may attend premises and take control of goods on the HCEO’s behalf. County Court bailiffs are employed by HM Courts & Tribunals Service and enforce County Court warrants.