> OruxMaps will go down to 1:25k OS maps, too. It doesn't have any maps 'on it', but is able to download maps from all sorts of places, to cover many geographic areas, including Britain.
Someone has been putting legal pressure on the developer of OruxMaps (probably the OS), so the latest version has had access to Bing OS maps removed ('blacklisted' in the software, in fact). The last version to have access to Bing OS maps is 5.5.3, which can be found on places other than the PlayStore...
Having just bought a Tesco Hudl, I've been playing with OruxMaps using GPS and compass (that I've not had access to before), and these show just what a great app it is, with so many nice touches. For instance, with GPS on, the map is centred on the GPS position, but, if you drag the screen, it will project a line from the current GPS position, and show distance and bearing, and then snap back after a few seconds. You can orient the onscreen map according to the compass reading or GPS heading (as well as the usual 'north up').
You can plan routes on OruxMaps, save them (and export/import as GPX), and follow them, log GPS tracks, all the usual stuff. My only niggle with route entry is that it doesn't yet allow route edit on the device, although you can move waypoints (they're separate from, but associated with the route).
Given DEM data, it will drape the map over the terrain (with a setting for vertical scale factor), and allow you to rotate and tilt the view. This works remarkably well on the quad-core Hudl.
It's massively configurable, and supports other sensors I don't have (ANT+ things), and facilities I've not yet tried.
For free software, it's fantastic. I might even have to make a donation...