To produce the GPX files on the OSM wiki I wrote a program to wrap the conversion/splitting process, which uses MapWinGIS as the GIS engine. The transform I declare for the input files (straight from OS) is "+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +towgs84=375,-111,431,0,0,0,0 +units=m +no_defs" and the projection I request from the reprojection is "+proj=longlat +ellps=WGS84 +datum=WGS84 +zone=30 +north +no_defs +towgs84=0,0,0"
Does this help? If you have a QGIS project you could share I could look at it from that angle.

What is your ultimate source? The existing admin boundaries come from the OS. I guess any misalignment could be due to the transform applied from OSGB to WGS84. I know I spent quite some time on getting the right transform - there are various versions in circulation. The transform I use aligns with the results that others get, and aligns nicely with natural features etc.

oops sorry, I see that you have reused the existing nodes, but you have moved them over... Interested in the background to that!

Hi Jack, thanks for sharing the ways between the admin and ward boundaries! I notice your boundaries seem a bit offset by a few metres compared to the OS boundaries... Is that the reason you delete the existing nodes and create a completely new way instead of just splitting the existing one? I would like to understand where the offset is coming from though... Can you point me at your source and/or send me one of your data files?

Hi,
I have adjusted this ward boundary to follow "accepted good practice" by sharing a way where it has a common boundary with other admin/political areas. It would be appreciated if you could follow this model... If you have any questions please feel free to ask.

And are you sure that it's ok to add data from the OS API to OSM under the terms of the OS API Licence?

Hi,
Please note that electoral wards should be tagged as boundary=political and have no admin_level. See boundary=political for more info.
Also, where a ward boundary coincides with a borough boundary, it's good practice to reuse (parts of) the existing way and nodes.
Good luck with mapping all the wards in London!

Sorry, that was meant for the creator of the relation

Hi,
Please note that electoral wards should be tagged as boundary=political and have no admin_level. See boundary=political for more info.
Also, where a ward boundary coincides with a borough boundary, it's good practice to reuse (parts of) the existing way and nodes.
Good luck with mapping all the wards in London!

Hi Brian, please be aware that some of your work around the river Corve appears to have been removed by a new mapper in changeset changeset/109539763
Not sure what's going on here exactly....
Regards, Colin

Hi... Should this not have name=Birtley? It seems strange to have a place, a town as well, without a name tag.

Hi.... Any particular reason to delete the Egglestone Abbey place=locality node?

Why did you do this? You have deleted perfectly normal, and correct, data. Please revert this change!

I would suggest the railway=crossing where this byway/road crosses the WCML might not be appropriate here, as the road seems to cross the tracks on a bridge. Railway=crossing is used for level crossings.

It looks like this one is clearly intended to cover the foreshore, extending down to the admin boundary at MLWS. http://www.norfolkcoastaonb.org.uk/content/maps/map-sections.php

If this was me, I apologise and I will fix it up! I have never found any "evidence" (in the broadest sense) whether an AONB, or National Park or similar includes the foreshore or not, so I tend to follow the precedent set by the creator of the protected area. It gives a very inconsistent picture across the UK, but it's not really my area. I wonder if there is some general jurisprudence on this, or if each protected area is determined separately?

Thanks for trying to fix it up. It didn't work very well, unfortunately as the boundary you added back was nowhere near aligned to the official boundary. It's sorted now, but please be more careful with boundaries in future.

Hi... I don't know if you realise what you have done, but you have deleted a large section of the boundary between Brize Norton and Carterton. Can you repair this please? If you need help, let us know here.

Hi... Where did you source the boundaries from for Runcorn and Widnes? They can't be tagged as admin boundaries as there is no admin function at that level - there is no Civil Parish. And the council name should not be given, for the same reason - Halton BC already covers these areas. Can you please sort this out? If you need any help feel free to ask.

My apologies Andre, I see now that you did not introduce the coastline tags here. I will look into benoitdd's changesets in the area.