Am I entitled to paid holidays?

I am a casual worker in a cafe in the UK. I work 6 hours a week. I am 17.

I recieved a text message from my boss today saying that I am not entitled to paid holidays because I am a casual worker. Is this true?

I can't afford to lose 2 weeks wages, but I have 2 weeks holiday at the moment. I took these holidays under the impression that I would be paid for them. If I knew I wouldn't be paid I wouldn't have taken the holidays
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