GPS coordinate interpretation.

I'm currently geotagging my pictures using HoudahGeo, before importing them into iPhoto.
I've noticed an issue with a few pictures, notably ones taken near the Greenwich Meridian.

After tagging an image, in iPhoto the location shows as
51 deg 30' 13.88 N
0 deg 0' 28.62 W

That looks about right to me, i.e. just to the West of the Meridian, on dry land.

When I go to FlickrExport and check the photo location it shows as
Lat: 51.503857
Lon: 0.007949
That seems to be to the East of the meridian, (in the middle of the Thames!) i.e. it ought to be -0.007949

I suspect this is caused by the EXIF data being put in by HoudahGeo not having a GPSLongitudeRef entry, just a GPSLongitude. There's a Ref entry for altitude but not for Long or Lat. I'll ask them about that.

According to the Exif inspector in Photoshop, the entries are
GPSLatitude 51,30.23
GPSLongitude 0,0.48

However, it would appear that FlickrExport and iPhoto are interpreting the data differently, with iPhoto showing the reading to the West and FE showing it to the East, which is inconsistent.

I'll ask the HoudahGeo folks why they're not giving a GPSLongitudeRef as having that may fix it, but I thought I'd raise that iPhoto and FlickrExport are interpreting the same data differently.

Edited to add: I've just re-run the workflow and HoudahGeo is definitely putting the wrong location in the EXIF, Preview's "locate" shows the wrong location too, and further examination of the EXIF shows an "E" tagged on on the end of the Longitude.