[OSM-newbies] josm downloads

[graham]

Hi,

First time use of josm. I want to download the hounslow area (west 
london). I go to openstreetmap.org and get the url:

http://www.openstreetmap.org/index.html?lat=51.47500724483292&lon=-0.35823974430907213&zoom=15

I get the download input box from the connections menu in josm. It comes 
with the url and bounding areas prefilled with lat and lon of zero. I 
delete the url and past in the url above. The min-lat and max-lat boxes 
auto-reset themselves to -22.5, +22.5; the min-lon and max-lon to -45 to 
+45. I can see no sense in this and manually delete the contents of the 
4 boxes. As I do so, the url I pasted in is reset to mlat 0, mlon 0.
I empty the 4 boxes, and repaste in the url. There is a red message at 
the bottom 'Download area too large, will probably be rejected by server'.

I try to download anyway and get an error message "the maximum bbox size 
is 0.25 and your request was too large. Either request a smaller area or 
use planet.osm" (error message alerts always get sent twice for some 
reason).

I try again, zooming closer, or leaving the contents of the lat/lon 
boxes with the apparently random values they auto-fill with, or trying 
to guess at possible values and enter them manually. Whatever I do I get 
the same result. Eventually I start getting a new error message: "error 
while parsing: attribute name not followed by '='". This is clearly 
wrong: the parameters on the url I'm inputting (above) are visibly ok.
Restarting josm gives me the same thing.

I haven't tried changing to planet.osm, as I'm not clear how to set that 
up and in any case I want to download gpx traces which the wiki says 
planet.osm doesn't have.


I'm obviously doing something stupid; what is it?

Thanks
Graham