I am not sure whether it the same for eZ 3.4.4,but on eZ 3.8.3 the variable $node_id is available in the template tipafriendmail.tpl and in the template itself the node_id is used to fetch the node object itself. So the only thing you need to do is to add the html for the display of the node to the tipafriendmail template. No PHP is needed, just template language like for every other template. Just have a look at the other templates you use to display a node to get a good starting point.
Ok, many thanks for that Claudia, you now have me on the right track.
I still have a couple of problems however. All emails sent all include the paragraph.tpl file from design/standard/templates/content/datatype/view/ezxmltags/ This, of course, gets translated from a html paragraph break to <p> tag on the emails. How would I get around excluding the paragraph.tpl from the tipafriend section? Could I make the tipafriend section html friendly?