Sorry for the brokenness of the last post, I am having trouble posting with .Text Right now I can't post more than 1800ish bytes...
[EDIT] I found the solution to the problem. I started investigating with Wireshark and the traffic looked odd - not normal HTTP packets - almost as if it were encrypted. So, on a gut feeling I tried posting using https://geekswithblogs.net/mikethomas/admin/EditPosts.aspx rather than http://geekswithblogs.net/mikethomas/admin/EditPosts.aspx and all now seems to work.