oli,
If your Blackberry runs Windows Mobile you can try Pocket FMS which is a very good interactive moving map display. If you want a basic moving map based on CAA charts you can load Memory Map. You will need at least 1Gb of memory to load both of these.
I use both (+TomTom) on my HTC Touch Cruise. Pocket FMS is my preferred option but I am having a few issues with the program locking at the moment so I have reverted to 1:500k CAA charts via Memory Map.
FNW