Except I recently used a postcode and ended up in a road of the same name in the next village (1.5 miles or so) which I was then told happens all the time 
That happens to me quiet a lot, in fact more and more as years go on, and you dont necessarily have to be out in the sticks for it to happen.
Problem with Post Codes is they change or more commonly get updated on daily basis, so your only as good as your last update, unlike a National Grid Reference which will never change. Post Codes are just that, a system originally designed for the Royal Mail sorting office with the first 4 digits given a good indication of where something is for someone in the know.
Personally I never understood why we dont use the NGR System, ok, asking someone to remember there Lat and Long is probably pushing it, but a 10 digit NGR is accurate to 10 cm anywhere in the UK, it can shortened to 8,6,4 digits very easerly, a 6 Digit NGR is accurate to 10m which is smaller than your average size House, and it can be found with a Sat Nav or just using a Map / A to Z and a pencil.
You often hear horror stories of Emergency Vehicles driving up and down country lanes to to find somewhere using Navi's, I would have thought to get an Ambulance within 10 m of a NGR of where it needs to be is pretty much job done.