Slightly off-topic, but relevant ...
Buy an HP 4700 PDA (there's one on EBAY right now for £90) : a tiny bluetooth GPS (e.g. EMTAC TRINE, £40) : and an extended battery for the PDA (£10).
You get a superb 4", outdoor-viewable screen, and the combination above will give you about 7 hours (yes, really) of usable time running Memory Map CAA VFR charts. It works beautifully - I've been using this combination for about 4 years with absolutely zero problems.
You can also run Tom Tom, Oziexplorer, Pocket FMS and a whole load of other stuff as well ....