You are entitled to be paid for work you have done. You should take advice immediately as to the best thing to do. Do not delay because employment tribunal time limits are very short. Speak to your trade union, or to your local advice centre.
You should also contact the Acas Helpline (tel: 0300 123 1100) as soon as possible. With your consent, a helpline adviser can refer your case to National Minimum Wage enforcement officers at HMRC who have powers to collect arrears on your behalf, to fine your employer and to include their name on a public list of employers who don’t pay the National Minimum Wage.
Acas early conciliation is the first step of all employment tribunal claims. An Acas conciliator may be able to persuade your employer to pay your wages without the need for you to bring a tribunal claim.