I am working on Open Sea Map and I need to download it for use on my GPS. In the past, I have downloaded the UK coastline and marine marks using http://xapi.openstreetmap.org/api/0.6. This has become so slow and unreliable, it is just about useless. 
Is there a better way to download the full UK or other large areas?
For full countries, you should use Planet extracts. See http://wiki.openstreetmap.org/wiki/Planet.osm#Downloading
Geofabrik provide extracts for most countries/regions in Europe. See http://download.geofabrik.de/osm/europe/
They donât seem to have an extract just for the UK, but there is extracts for âBritish Islesâ or âGreat Britainâ, plus separate ones for Scotland/England/Wales etc.
Discovered this shortly after posting but thanks anyway. Now I just need to work out why osmosis encounters an error when I try to filter seamarks out of the Great Britain file. It works for just scotland so I probably just need to do it in smaller sections.