I can understand some confusion over the behaviour of group messages. Sounds like there are three main points here, so I’ll break them down like this:
Group messages appearing in inbox, not category views (no unified view)
Mechanically, group messages are simply private messages sent to people in the same group. In this sense, groups are essentially little more than private message mailing lists. There’s no way to make group messages appear in categories without moving them individually to a public category.
Something we’re considering for bigger and more active groups going forward is creating private categories - a standard category only visible to members of that particular group. This would allow for a lot more flexibility (e.g. the availability of subcategories) and a more unified experience for those group members.
Default view for groups (navigating to group messages)
I agree it’s a bit of a pain navigating to the group inbox through the group page. I don’t think there’s much we can do about that unfortunately.
That said, I find the quickest way to view group messages is from my inbox (clicking on my profile picture then on the envelope icon). From there it’s possible to see all group messages as well as other private messages - you can filter these by group if easier. It’s also possible to send a group message from there by clicking on the New Message button and typing ‘London’ into the addressee box.
Navigation to/from Talk, Fixometer & Wiki
I see your point here - I haven’t added a Talk link to the top navigation bar because clicking the logo does the same thing. And the reason the logo links to the Talk homepage and not the Dashboard is that the mobile theme doesn’t have space for any links at the top 
I’ve put a link to the main dashboard (Fixometer) in the hamburger menu so that mobile users can find their way there, but my feeling is it’s more important to provide mobile users an obvious way to return to the Talk homepage (by tapping on the logo).
Ultimately, it’d be great to have the same bar running across the top of all parts of restarters.net. But again, we’re not there yet and we’ve definitely still got some thinking to do about how best to integrate the different elements of restarters.net in the meantime!
We’re definitely open to suggestions 