Recently I relocate to the UK and stay there and as a debt adviser, I found that they have two types of debt collectors where one has the legal power and one does not have it. So the Bailiffs are Enforcement Agents and they have the legal right to visit your property and sell your assets to pay off the debts. But the Debt collectors are often referred to as doorstep collectors and they work for or on behalf of a creditor.
A Bailiff loans money to a person on bail, (temporary release) from a jail sentence.
Debt collectors call, email, mail and just make themselves irritating to collect money owed to their client. A Bailiff could employee a debt collector to recap lost bail