I just can't hold back from singing the praises of a new app for Android phones.
Take a look at AlpineQuest. The free version gives access to Openstreet map maps with contours for the world, paid for (best £4 ever) gives access to full 1:50k and 1:25k OS maps!!!
The app does not need mobile signal in use, just pre-cache maps at home for the scales / zoom levels you want on WiFi then good to go.
I imported some GPZ files for this weekend, and used the app in real life for 1st time. What a fantastic experience. Battery life is excellent, only used 20% or so over a 5 hours family/group plod with regular map checks.
I reckon the purchase of one of these to use on a 2nd hand mobile just used for this would be perfect.
My usual GPS is a Garmin eTrex HCx by the way, and it didn't get a look in this weekend.
Can't rave about this app enough for £4.