Which Handheld GPS system specifically for hiking in the Lake District

I am keen to purchase a stand-alone system for hiking (in fog!) in the UK Lake District. I'm not interested in systems which don't display OS maps (the idea of picking up a map reference and then getting out the map in the rain and wind seems to defeat the object to me!)

I'd greatly appreciate advice on a system which will achieve this - it does not have to have any other PDA or comms features.

So,

- UK Lake District or other mountain regions
- 4-5 hours battery life or adaptions to make this possible
- rugged and dependable
- Map display (preferably colour)

What would you recommend? All price ranges considered.

Thanx!!!