What should I say I expect my salary to be in?(GBP)

I'm applying for my first ever job. It's as a warehouse operative. It's part time and about 30 hours a week with flexible hours. The application is asking what I expect my salary to be and I have no clue what to put. Anyone able to help me out? Also if you have an answer I'd really prefer it in British Pounds to make it easier for me to understand. Thanks

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