Basically is it worth 400quid to not have to get a map out at every crossroad so routes can be planned on the computer and followed accurately
Doesn’t have to be £400 … but absolutely. The problem with maps, is you’ve all too often overshot your turn-off by a couple of miles and descended a massive hill before alarm bells start ringing and you decide to get it out.
With GPS, it just takes a quick glance (providing you’ve panned your route beforehand) and you will know if you’re still on your route or not. Maps are all well and good for walking, when you can read them on the move, mess about with your compass and all the rest of it, but (and I’m sure I’ll be flamed by the purists here) they can be a huge chore on a bike, potentially adding hours to your journey time.
You still get to play with maps, when you plan your route initially. And there’s nothing wrong with taking one as a backup. But I’d be lost without my GPS now. Quite literally. It’s probably one of my favourite bike related items.
For navigation I usually use an Etrex 20, which is great. A fraction of the cost of an Edge 800, I think it was designed primarily for walking, so excellent navigation but also includes all the basic cycle functions, and even an automotive mode I quite like.
Cycle specific units like the Edge 800 include a lot of training functions, as well as heart rate / cadence abilities, etc (which are bought separately). All stuff you may, or may not want. If you just want something to find your way with and record your routes, the Etrex is more than enough.
Edge 200 and 500 I wouldn’t recommend for navigation. They’re OK, on easy to navigate routes to begin with…sometimes. But their real strengths are in the endless reams of data they output.