Another option (and it requires some "fiddling" of the TomTom is to try TomTom Offriad Navigator.
It's not written or endorsed by TomTom, and although I managed to get it working on my One XL, I couldn't input numbers (as the input screen was scrambled). Also, some of the pages on the website are French.
http://www.webazar.org/tomtom/offroad.php?lang=uk
Good luck. I don't recommend this, but it might be a cheaper way out.