Hi,
I assume you found the file to edit as you get error messages about missing fields.
Your issue is quite easy to fix without any php skill: you have to keep those fields but just don't show them to the user, and the html code may look like:

<input type="hidden" name="field_to_hide" value="forced_value" />

You should replace the original code by this one, field_to_hide by the name of the field you don't want to show and forced_value by the value you want to enforce (may be empty if you dont wan't to use the field)

Thanks madz, I'll give that a try. Yeah, I know exactly what files I need to modify. I tried just assigning a value to the fields, but that wasn't working. I should have mentioned that my html form coding skills aren't so hot either :). I'm great at modifying code, but it's harder to write from scratch!! Much appreciated.

Thanks again. I have it working very nicely now.