As Toureman says, you need to explain what kind of entrance you want to obstruct. The law still stands that makes it illegal to park on a public road, but that law has not been enforced for many years for obvious reasons. For an offence of causing an obstruction, the prosecution would need to prove that you are preventing someone from making a lawful journey and that your action was unreasonable. If someone has a garage or parking space, they are entitled to use the highway as far as it extends and that includes crossing (but not parking on) the footpath. So, you have no need to worry about parking in front of someone's garden gate if you have left room for a pedestrian or wheelchair user to reach it.