Drake wrote: So i was "encouraged" to purchase a sat nav(tom tom), and i must admit my views on this technology has changed .
So this has made me wonder how good cycle sat navs are . Are they similar to motoring varieties . . i.e with similar displays etc.
I too have found car SatNavs excellent for many purposes, for example they excel at finding a hotel or business address in the middle of a city I have not been to before and best of all, they allow me to focus on driving and not have to drive with one hand while reading a map with the other. (Which of course I never did Officer...)
For getting around locally I don't bother as I know better routes.
However, I am not aware of a SatNav for bikes which you can use in the same way and that is because choice of route on a bike is not just more difficult but also to a large degree a personal thing - I would avoid busy roads like the plague but others seem happy to ride along, for example, the A38 through Devon. So even where the device can plan a route for you it may not take you along roads you are comfortable with.
To the best of my knowledge to get the best out of a GPS enabled device on a bike (assuming you want it to take you somewhere as opposed to you just riding along and the device recording where you have been) you have to pre-plan your route on a PC using a variety of tools, including free websites such as bikeroutetoaster. The screen on bike-sized GPS devices are just too small to see anything other than a tiny section of the route or in some cases they don't show a map at all.
Once you have your pre-planned route you can upload it to your GPS and then either through a moving map or turn-indicators it will do its best to guide you to where you wanted to go. However, as with car GPS devices, be prepared for the thing taking you down a blind alley, so to speak. You can't switch off your brain as roads can alter faster than the maps.
For what it's worth, I uses a SatMap Active 10. These have come down in price a lot recently but as they seem to be all sold out that is not much help I guess! It has a proper moving map (in this case 1:50K OS mapping) and can both record details of the journey but also, and very importantly for what I want it for, accept a pre-planned route and display it as an overlay on the map. It came with a proper bike mounting and has proved very robust and weather-proof. It uses buttons for control which are much easier to use when riding than a touch-sensitive screen as you can find them without having to look down once you are familiar with the thing.