Need help with British (vs. US) English

Need some British-speak help. Here in the US there's a phrase, "hand caught in the cookie jar" which basically means you've been caught doing something you shouldn't. I like it for the scene I'm writing because it suggests a kid or someone who is young getting caught. I THINK what we call cookies are called biscuits in the UK. If so, it seems unlikely that you'd use the same phrase. What other phrase could I use?

Robson's first name?

Do we not know Robson's first name? I thought it was Philip but the Buffy wiki pages don't list a first name for him at all and so know I'm thinking I was wrong.

Ripper trailer

I was looking for a pseudo-trailer. If I remember correctly it was a tv series about a young Ripper and his friends. Didn't find it but stumbled across this instead.

"Tea Making Tips (1941)" (Watch on YouTube)