Which of these was particularly important in creating a large proletariat in britain in the 1700s?

That would be enclosures.

Up to 18th century in the Great Britain farming was by and large done in the open fields that everyone from the village used. That changed when the large public areas were enclosed that is fenced off and no one but the owner could use it. So the people now worked for a wage on someone's land thus bringing the creation of the proletariat.