We are fairly new to geocaching and bought a Garmin eTrex Summit. We'd like to go paperless by downloading descriptions to our Android phone. Our Summit only seems to function on the British Grid and the geocaching apps don't bring through the British Grid references.

So I telephoned Garmin telling them that my Summit when set to "Position Format" - hddd.mm.mmmm and "Map Datum" - wgs84 sends me and my family 17 miles in the opposite direction. Whilst the poor Garmin technical bod had me on hold for the third time and was having a nervous breakdown, I changed the "Map Datum" to Ordnance Survey GB. It now seems to work.

Is the GPS faulty? Do I need to update it? Any clues gratefully received.