> English Empire

You mean British Empire.

The Act of Union had at least two willing parties.

Actually they weren't. The majority of the populations of Scotland and England did not want it in 1707. There was rioting in Edinburgh when it happened and the signatories had to go into a cellar to hide from it. Most English people didn't want to annex Scotland either, since they thought it threatened their trade.

Under 0.01% of the Scottish population had a vote for the parliament in the first place. The Scottish politicians were bribed and there is a document showing how much each was paid (which is ridiculously hard to get hold of online, for some reason.)

The English parliament continued with a few extra members, while the Scottish parliament was abolished. The speaker of the English parliament boasted, "We have catch'd Scotland and will bind her fast."