h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Hello!
This came from a random conversation I ended up having a few days ago. For some reason, the conversation got steered to old tv programmes we watched when we were all younger. I suddenly remembered this show I used to watch when I was wee, but I now for the life of me cannot remember what this show was called.
This show was from the 90's, and I think was shown on CBBC. It was a gameshow. It involved kids in a lift in a building somewhere, and they had to speak to this head on a tv screen (like the tizer head I recall, but with yellow hair). In this show, the kids had to do various tasks to win prizes, but the one that really sticks in my head is this game where they were 'shrunk' and had to swim in a bowl of alphabet soup in a massive studio kitchen. My mate also remembers a game that involves something like a chess game involving a guy dressed like darth vader, and you won prizes at the end of it.
Before anyone decides that I am on something, I have asked about my friends, and the answers to this description are along the lines that people either do remember the show or don't, so I'm sure it isn't due to something in the water at that time...!
If anyone does remember the name, I would be very greatful! Any other information would be appreciated.
Thanks in advance!
Macphisto