* Would Watt and his investor have built steam engines without the patent?
  * Did the patent enable Watt to create a market which otherwise did not exists?

To argue that patents were overall beneficial, one has to argue that without the patent, steam engines would not have become popular, and for that two things would have had to be true: 1. Watt would not build engines and 2. Nobody else would build them either. There is an argument that nobody else would have built them because there was no market, and only Watt's patent allowed them to create the market. Except that to believe that, one has to ignore the fact that a) England was undergoing the industrial revolution in all aspects (not just steam engines) and b) there was a huge need for industrial power removed from water wheels. Watt did not invent the steam engine. He invented an improvement, simultaneously along with many others. But only he had the clout to get the government to enforce his patent.

So its not hard to say "whether overall the English patent system facilitated that process": it most certainly did not facilitate that process, and the "temporary roadblocks" you describe were demonstrably the only effect, and a negative one.

To argue "the english had the most dramatic industrial revolution and the english had a patent system, therefore the patent system caused the industrial revolution" is to ignore the political, economic and scientific history of the country.

Edit: this bit is my opinion: England's supremacy is entirely due to its separation from the catholic church: it generated a need for military supremacy and at the same time freed the minds of thinkers to be scientific. Do you think Cambridge scholars had to worry about being locked up by the inquisition like Galileo?