Just found this free map application which has full OS detail on my GPS phone. Looks like you can use it for off road navigation.
Any one else using the Orux map app, and is it of any use? Ta.

Haven’t used that app but I can suggest you look into mm tracker.
It is a very good application, based on the memory map software and has the functionality of a garmin edge.

I use it. It’s not the most intuitive app, but it’s the one I tend to use most, and the most “tweakable”. You’ll need mobile atlas creator to create any offline maps you need (which is pretty straightforward if you read the instructions). If you don’t, then it will try to use your 3g connection to download maps over the air – which will reduce your battery life or leave you lost somewhere with no signal.

Not tried MM tracker though.

Others I’ve still left on the phone are :
Maverick (paid) though there is a free version. Looks good and a simple UI, but it’s a pain to use.
Multimap
OS map