Garmin Edge 705 - which maps to add?

[NobleLord]

I've just bought a Garmin 705 and have been told that the base mapping it comes with as standard is not much use at all. There's plenty of talk on various forums about adding maps on an SD card. Having Googled it a few times, I can't seem to find any decent info on which maps are compatible and how you buy and upload them to the unit.

Basically, I'm after a decent road (maybe OS) map on the unit so that I can plot courses to cycle using something like RidewithGPS, then set off and have a half decent reference map on the unit. I've heard of things like Multi Map and the like, but don't know if they're compatible with the unit.

Any advice welcome.

Thanks,
NL

[rhinochopig]

I bought Garmin Mapsource for my GPS60csx and a 2 gig card. It means I can fit all of the UK topo mapping onto my GPS. It's good enough for most things but does not replace an OS map as the detail isn't there.

Think it cost about £60.