Glad to be of help. I can't see Ovivo lasting forever, but they've been going a few years now. The SIM only recently went up from £15 too.

I believe the Memory Map application is free, but the maps are very expensive. See here.
You buy the maps you want and then you own them.
While there are Memory Map apps that run on IoS and Android now, the company left their customers high and dry for several years producing no mobile app on any current platform. Users were very unhappy and turned to MM Tracker in droves. Memory Map finally published an IoS and Android version of Memory Map last year. The previous version ran on Windows Mobile 6.x, which dates back to 2007.
The older OS maps were not encrypted and were extensively pirated.

If you're looking for alternatives, I wrote this blog in January. You can create perfect, free OS 1:25K maps for a mobile device. The catch is that you need a Magellan eXplorist 510, 610 or 710.
If you want OS 1:25K maps on your PC to plan routes, there are free web apps of course, one even comes with Geocaching Live integration.