Yep – thats pretty much what I ended up with. I went with something like this
request = FtpWebRequest.Create("ftp://ftp.whatever.com/somefile.txt");
request.Method = WebRequestMethods.Ftp.GetDateTimestamp;
request.Proxy = null;
using (FtpWebResponse resp = (FtpWebResponse)request.GetResponse())
{
Console.WriteLine(resp.LastModified);
}