GPS can be really useful for allowing map-checking on the move rather than constant paper map faff. Did 3 days of riding in the Brecon Beacons recently and didn’t look at the paper maps once. But they were there in the backpack in case of GPS failure.
Get something that has the maps stored in memory before you start. Smartphones that download the maps as you move around are fine, until you lose phone reception, and then you’ve got no more maps.
I use a Satmap with 1:25000 and 1:50000 OS mapping, but there are plenty of other good units out there from the likes of Garmin, MemoryMap etc.