BB is partly a game and it can be a tense one for the HM and the audience. The tension comes from the voting patterns and the difficulty people have in deciding who to vote for. If the public supports some HMs (which is a way of saying it is a succesful BB) they share the tension as their favourite is nominated or not. Because alliances are not allowed in UK BB people are nominated usually for some reason supported by enough of their fellow HMs. Nominations day is the test of where the friendships and fault lines lie in the house. Nominations day is also when the decisive questions are answered. Will Darren change his vote and remove Mel, will Adele and Alex nominate Kate against Spencer or Jonny, who will Jade or Brian pick now they have the deciding vote, who will nominate Spencer?
Head of House ruins this. The winner of some task (and the tasks on UK BB have recently been childish and random) decides what he tactically or emotionally or randomly wants to do. There is no guarantee that he won't nominate all the females or all the favourites or all the interesting people so all the current problems remain. The choice may still be misguided (jon Tickle would always have nominated Cameron and who ever else was nominated would always have gone) The decisive choices for the game now become either more predictable if a committed person makes them or random if a neutral person does. The individual choices that each HM has to make each week are avoided (Brian over Josh, Adele over Jade, Kate over Jade,, Alex over Kate, Kate over Tim) and all you get is one person deciding. What is pretty certain is that the great standoffs of the past would have been unlikely - its very difficult to get an Alex-Spencer competition in BB3 with a HoH deciding one or both nominees . in BB3 Jade would have gone out to almost any HOH, Adele would have survived as only Jonny or PJ would have removed her. A tactically minded HOH would have put Kate, Spencer, Alex and Jonny up until only one was left and we would have known the winner as soon as the last vote was completed.
HoH just destroys the working out of the story. Imagine BB3 if Alex, Kate and Spencer have all gone and Jonny is left with Adele - who would be watching if 3 of the favourite characters had gone becausesomeone (say Jade) had won pass the parcel twice before she went herself? . It works in America because voters there are not part of the story and because the US game is a blatantly tactical one where nasty people can win. All you gain in the UK game are a few tears from Ray and a random outcome - such as when he took Nush out and left us with the total boredom that was Steph. its Bad Bad Bad and a poor substitute for a good theme for the show.