No I'm not sure, so I'll sit corrected. (Can you guess, I've never used it?)
Alternatives to Memory Map - they're all much of a muchness in that OS is OS, and all have quirky * UIs. (* quirky is being polite)
But you might find bundled deals with Tracklogs, for example.
Mem Map is particularly attractive for those who spend time in France, as it does IGN as well as OS, and very cheaply too.
Mapsource - agreed the rendering is hard to stomach at first, but even so this is what I use because:
* offline
* maps match what will be in the GPS (eg junction locations are identical)
* great detail coverage (to house number level) of W Europe (Metroguide or City)
* coverage of anywhere in the world (by adding OSM maps)
* very good Track handling (cutting / reversing / joining / downsampling etc etc)
* very useful 'snap to map point' feature (a point placed on a junction sits
exactly on that junction - this is very noticeable later, and very solid-feeling, when you are following the route on road)
* best interface with GPS (especially Etrex) for transfer of data.
Downsides -
* poor rendering, see below
* poor tool set overall, has to be supplemented by using other software, notably WinGDB3
* routepoints (or 'via' points) uneditable
* routing, if you use it, can be misleading (does not match GPS)
* fussy with mal-formed files (many imported GPX files just show an error)
* more or less abandoned by Garmin now, in favour of BaseCamp
Rendering -
Mapsource probably installs to an early version, typically v6.13 or lower. It can be updated using the latest version from Garmin's site, and this offers what I would describe as 'different' rendering. 'Different' as in, what is newer is not always better. NB that the very latest version also requires XP SP3 or newer.
You can see screenshots of both renders side by side, and read more about upgrading/downgrading Mapsource,
here