Clip from 2008. Dwayne Cameron played Lindsay Reynolds with Harry McNaughton who played Gerald Tippett. As far as I can tell the two of them had a one-night stand only. Harry's character appears to have been an asexual person through most of his run on the show.
I knew there were some scenes missing from Henry and Seth's storyline so I did some digging. I don't know how to edit video but here are the dates. I think you'll find Dailymotion has these clips. These also explain why Seth was so angry with Sarah. God she has a mouth on her.
Henry's first appearance as Seth's boyfriend
1) Shortland Street - Episode 5115 (26 October 2012) 2) Shortland Street - Episode 5116 (29 October 2012) 3) Shortland Street - Episode 5117 (30 October 2012)