Nicole Scherzinger will play Keith's vocal coach while Hunter from challenge show Gladiators will also make an appearance.
Marvin Humes warns ITV viewers to look out for his... "dodgy American accent. Expect a lot of collar flicking, and a lot of rubbing my hands through my hair, which I was very, very proud of as I'm getting a bit thin on top. To have a full head of hair was amazing."
Louise Redknapp comments: "Apart from being delirious as we filmed on the coldest day of the year, the funniest moment of filming was watching Keith trying to get on a pair of thigh high PVC boots in a pair of mittens!"