Hmm, I don't see anything strange at all in either of those screenshots and your organizational stuff looks fine. I noticed that in your menus screenshot, your submenus are not setup there, but on the front of the site, they are (though I suspect that the theme probably adds the child pages automatically).
A little bit about the "-2" addendum. WP automatically adds a -2 to the slug of anything that already uses that slug. It is most commonly seen in tags and categories, but also effects pages and posts too. For example, say you create a category called kitchens. A few months later, you attempt to create a tag, also called kitchens. The tag will be created, but because the slug was previously used by the category, the slug for the tag will become kitchens-2.
I suspect that at some point, you created a second joinery page and the -2 was added to the slug, but then you changed the title of that page without making the change to the page's slug.
Here is where you will find the problem...
The page you did this to was your Home page. Without seeing it, I can guess based on two behaviors: 1) Attempting to load http://marcuswhitehead.co.uk/joinery-2 redirects to the homepage - because you have that set as your home page. 2) The URL for the child pages includes joinery-2 and they are setup as the child pages to your Home page. Parent page slugs are included in the child page URLs. You will find joinery-2 in your dashboard as the slug for the Home page.
Solution: Update the slug for the Home page to read as home, or something appropriate for that particular menu.