John, I downloaded the Grid Reference app for my HTC phone (£4) and really like it, great recommendation The OS maps offline are great as is the Compass button in GPS mode for easy access and of course - BIG NUMBERS for easy outside reading.
How accurate do you find it?I tried out a free version but the GR was out by a few hundred metres.If this one is accurate, please let us know. You have to be able to trust it.Cheers and have a great weekend.M