I use a Garmin 450T on the trails. The best maps are Garmin GB Discoverer 1:50000 (all of UK, or they do regional maps and maps of the NP's)
Thanks for your post and info.
I now have the latest Garmin GB Discoverer (Land Ranger) Maps.
The Oregon doesn't come with a mount, how did you fit your 450T to your bike?
I'm thinking using a RAM mount and the vehicle mount combined as the supplied suction disc thingy is for windscreens is obviously of no use on a bike and substitute the suction disc for the RAM mount.