This GPS unit with Ordnance Survey mapping is quite expensive (£320 on offer from Wiggle), but with the whole of the country available at 1:25000 scale, that's a lot of detail at your fingertips.
It has a USB interface and is powered by 2 AA batteries.
My name is John Swindells and I'm a keen recreational cyclist with a preference for long one-day rides. I've also previously dabbled in time trialling and cyclo-cross. See more of what I get up to on Strava!