Yes, and in fact I did download the data with josm first. The only issue was that I didn't trust it to merge things correctly. As a result I saved my "notes" in the form of another, overlay, .osm file while I was there and used that to copy & paste the larger items (mostly car park outlines) when I returned.

I've been having a bit of a fight with josm over relations and the South West Coast Path in particular, but I think I'm not too far from resolving that now that I've read some of the info which people have posted on the issue. I think probably josm is not keeping the relations and the ways in sync so that the upload fails if I make certain changes.

I think I should have that fixed shortly, and there are only a couple of small sections of path which are not currently quite correct.

I was staying on Lelant Downs in a very nice "cottage" called Golden Cock which you can see here:

http://www.openstreetmap.org/?lat=50.17422&lon=-5.44879&zoom=17&layers=B000FTF

I don't expect to get a chance to return to Cornwall this year, but I dare say a number of other OSMers will visit over the course of the summer and extend the map in that area.

I used to regularly visit Sennen as my Grandmother used to live there, but this trip was the first time in 15 years that I've been back to those old haunts. Its interesting to see whats has changed in the mean time, of course.

Yes, I did think about joining that mapping party, although normally I've been working in South Wales and I don't make it up that far North more than once or twice a year. Not sure what I'm likely to be doing in September yet.

My GPS is a Garmin too (Vista HCx) so I wonder if thats a Garmin specific thing, or whether its common to all of them (as I suspect). I presume that when it says "accurate to X ft" that its actually quoting a 95% confidence interval or something along those lines, but nothing in the docs seems to say.

I thought I'd be able to do a lot of the roads from the car, but when I've actually got to them I've often discovered that they are unsurfaced and thus only passable in a 4x4, so on foot will most likely be the only option. Plus the various telephone boxes, bus stops, etc will be an on foot thing. Still I've seen a lot of places I've never seen before by doing all this.