thanks Jason, little light bulb suggests path was keyed in looking at an example, and the pem file is in the linkpoint folder in the root, same as the confirm page.
So, now the pem file is being retrieved correctly, the transaction still fails, but the <keyfile></keyfile> tags now contain a value, which is the correct path to the pem file.
**Just a thought, this is my clients pem, will it actually work on my testing site ??**