After a lot more messing about I did manage to get the latest firmware installed, more by trial and error than by any other means, just kept doing seemingly the same thing until it worked.

That did enable a few more bits and pieces in the web UI, but I have to say compared to the other various routers I have used recently the UI is a bit of a disappointment. I have got used to being able to do everything I need via the web UI.

So back to the bad old days of configuring my router via the CLI

One example of something it won't let me do via the UI is assign a pre-existing IP address to a given MAC address via DHCP. It will let me fix an IP address once it has handed it out, but I have a set of MAC/IP mappings already that I want to keep. It looks like I can do it via the CLI, with lease times set to 0 seconds, but every other recent router I have used allows this sort of thing via the web UI.