Is there any other way to enable the shop module for just specific websites? It seems pretty crazy in v17 that this not an option in the system. We have to redirect a load of pages in order to disable it. Surely an option in the code and relevant checking whether or not add to the site map for that website if the box is ticked or vice versa would be sensible?

I guess this could be done as a module if not a planned feature already in the code?

Paresh is right, but a minor add on from my side. You need developer mode activated to find the Redirect Section under "Website" > "Configuration" > "Redirects". Also make sure to remove the menu item for shop on the sites where you don't want it to be disabled. For more information about multiple websites in Odoo see: 

https://jortdevreeze.com/blog/odoo-2/a-comprehensive-guide-to-running-multiple-websites-in-odoo-6

This solution is only redirecting 1 page. For example, the main /shop page, or /blog page. But this is not redirecting all products of the shop, or all the articles from the blog.
About e-commerce, Odoo is generating the sitemap, so all the pages are visibles by default to anyone.
What is the solution ?