Bailiffs typically cannot enter your home without your permission, but there are some exceptions:
No force: Bailiffs cannot force their way into your home, such as by pushing past you.
Hours: Bailiffs cannot enter between 9 PM and 6 AM.
Entry points: Bailiffs cannot enter through anything other than the door.
Vulnerable people: Bailiffs cannot enter if only children under 16 or vulnerable people are present.
Court permission: Bailiffs can apply to the court for permission to use reasonable force to gain access.
Magistrates Court fines: Bailiffs can use force to break into a debtor's property if they are collecting for a Magistrates Court fine in respect of a criminal conviction.
Unpaid tax: Bailiffs employed by HMRC can force entry if the debt is unpaid tax.
Trade or business premises: County Court bailiffs and High Court enforcement officers can force entry to trade or business premises.
If you're expecting bailiffs, you can make it difficult for them to enter by keeping your doors and windows locked.
But the most obvious and sensible way of stopping them is by contacting them to tell them that the person they're looking for is no longer at that address. You can do that either by letter (I recommend using Recorded Delivery) or email. You may then be asked some questions, such as when you purchased the property and who lives there, but once you've updated them, your address would be removed from their records.