@Nigelnaturist thanks for the info on the Bryton stuff. I'll take a good look. I like the idea of uploading routes to follow. Hrm and cadence also appeal . I was looking at the 800 really, but we'll see. Gear acquisition syndrome has taken hold, because I really fancy a decent bike too.
You can up load course files to the bryton site and then to the unit, I am not sure but you might be able to with Brytonbridge (software to interface with the unit), i found both the R35 and R20 very accurate on the GPS side, but like all the odd section can wonder from time to time, except if following a course and the gps is locked to the road (this is with mapping on the 705)) 800 ect so I guess it will be on there, however I cant say if you transfer a course file you created externally it will have all the waypoints you put in (Bryton units) should do but as its something I have never done I cant say, this is my ride today from the R20 unit it doesn't have thermometer so there is no temp shown, but i usually get that from garmin connect, however my last three rides its not shown, so I am having to use the data from sportstracks.
Bike well mines an 8 year old Viking Torino, its gone from 7sp triple to 9sp triple, still sorting out the best ratios, I think I have it sorted but it will have to wait till I can get a new cassette, I am happy with the 13-14-15-15-17 but I dont like the jump from 17-19 so i am going to change the 19-21-24-27 to 18-20-23-26 or 27, though I need a new RD my Sora 7/8sp one has worn out and has become a little unreliable on shifting, but most of all I want some decent wheels that dont go bang every so often