Have a look at osm.wiki/Importing_Government_Data for some ideas. Or you can use the mailing lists (osm.wiki/Mailing_lists) if you require specific help.

Hi,
According to osm.wiki/wiki/7th_Series User:TimSC is doing some collecting.
Also looking at osm.wiki/Provisional/First_Edition User:Blackadder is also collecting. So you might want to drop either a mail.

What did it say on the failure mail ?

Also have you had a look at:
osm.wiki/index.php/GPX_Import_Failures

The OSM wiki give a good overview of what you need to know. It can be found at:
osm.wiki/Map_Making_Overview

Had a quick look on the wiki and according to this page:
osm.wiki/Converting_GPS_track_data_between_formats
you have rte extension and looking at this page:
osm.wiki/Converting_between_formats
it is not supported yet.

But if you have a look at the various Garmin conversion programs, links can be found on this page:
osm.wiki/OSM_Map_On_Garmin
then you might find one of them "may" get you some way there, or you may be able to get them to help you.

Good luck :)

I had a quick try and it worked for me. Have a look at:
http://www.maposmatic.org/jobs/8451

The only problem is that I had to go in one more level than I would have liked, as it cut off some of the streets, but overall it looks as if it got most of the streets.

Have a look at the Wiki revert page for more info:
osm.wiki/Revert

If you are too impatient to see your edits you can go to the tiles@home server http://server.tah.openstreetmap.org/Browse/slippy/ and request it to render your changes, which should then become available under the Osmarender option on the main map.

Thanks will give it a try