Well as those of us in the UK know the mapping options for hillwalking etc are poor for us on WMP at the moment and those that do exist are frankly over priced pieces of rubbish that either have a poor os map or none at all!!!
So I looked around and didn't find a solution and then remembered a solution that I once used on WM5 before I started using Memory-Maps..
Tried it and works a damn treat and best of all it's FREE...
So here goes...
1)Firstly you will need to install Navicomputer from the market.. Get it set up and syncing with skydrive/onedrive..
2)Then get on Google and find MOBAC but one that still has the map-sources for ordnance survey maps it will be between version numbers 1.7 and 1.8. Not sure which one has it as my MOBAC is one have modded myself to included OS map-source and is app version 1.9.16.
3)Install it and then choose Ordnance Survey map-source and set to area you wish(TIP...use ovimap to choose/highlight large areas then switch to OS before you click add selection).
Make sure when you click new(to create file) you choose navicomputer. And let it do it's stuff.
Just beware as the files can be large depending on the amount of zoom levels you choose! and also move the Navicomputer and data to SDcard too!!!! (I use sense storage app to do this)
4)When finished simply upload the map file to skydrive, Yes I know there is a PC sync app for navicomputer but it simply doesn't work...
5)Now in navicomputer go to files click sync button, go to skydrive option and choose import offline maps. it will give you a list of map files(if you have created more than one) choose and download the required file and that's it..
You now have Ordnance Survey maps on the wmp!!!!
Best part is you can create as many maps as you wish and upload them to skydrive so you will always have access to them(if you have data/wifi access) and you can use any map-sources you wish so not limited to OS maps or OSM maps either...
Hope that helps you all..
If so please let me know and any further suggestions you have so can improve this little guide...