The simple answer is you just dont open the door to them.
They cant break down your door.
Climb through window etc.
Even if you do make a mistake and open the door to them just close it again they cant force there way past you to get inside.
That program makes me laugh how much it is edited in favour of them.
It never shows the times they turn up at properties and are told to go do one by someone that knows not to answer the door to them.
If they're there to evict you, then yes they can very much break down the door to get you out. If it's just a debt collection then no they can't break in - only make a peaceful entry. However they are allowed to seize goods that are outside of your property. So a lot of them will check the car to ensure it's not financed, and then clamp that.
I quite enjoy watching this program, and like the OP one case that made me wonder the same thing was some guy who owed some money moved back in with his Dad. Que the HCEOs turning up at his dads place and threatening to take stuff away unless he can prove the items are his and not his sons. His response was that a lot of the stuff in his house is 10-20 years old and he wouldn't have any form of ownership documentation.
One episode had a classic example of where this turned against them. They were sent to collect a debt of something like 0.5 million, and turned up at this rather large house (maybe 8-10 bedrooms),I think there was a Ferrari and a Lamborghini on the drive, and with no-one answering the door, they seized both cars. Turns out they didn't actually belong to the debtor and the cars had to be returned - i would assume the HCEO's had to cover the costs for seizure and return delivery.