Hi Alison
I have a 123-reg website with a similar issue. I have a form which sends info to a script which writes back to the site. Basically people can add themselves to an email list, at the same time I get an email to inform me of the entry. I have had continuous garbage entries onto the site and all the emails I receive come from various names all @sweb11.hi.local
I have taken the form down which sends the entered fields to the script that writes to the page and it still happened. I changed the web file attribute chmod to me only and it still carried on. I have more than one 123-reg site and strangely I cannot cross run the script between sites so I came to the conclusion that it was the server itself. I have only just done a goggle search on this which found your post so I will be giving 123-reg a contact.
Just thought I would post as another 123-reg customer.
