Any question answered...

Is a Garmin 800 worth the £107 extra over a 605? Both new. I care not for cadence, heart rate and so on. I just want to upload routes I've plotted in ridewithgps.com and get it to tell me where to go while recording where I go and how fast I go.

I have a Garmin 705, with Open Street Map rather than Garmin maps however- makes no odds if you plot your route before leaving.

You are welcome to borrow it, I have all the relevant sensors (for the bike- you'd have to supply an HRM if you wanted it).