Hello my name is ***** ***** I am happy to help you today. They do not have the right to withhold wages from you so that you are not paid for work that you do. You should write to them to say that they are in breach of contract and the National Minimum Wage Act and that to not pay you amounts to an unlawful deduction from wages. You should state that if you are not paid within 7 days you will raise a claim.
You will be able to commence the claim procedure using the ACAS early claim conciliation service. Details can be found at http://www.acas.org.uk/earlyconciliation
Please do let me know if you have any further questions, If I have answered your question I would be grateful if you would take the time to rate my answer. Thank you and all the best.