Hi Pooh,
As you have indicated in your question, a person who qualifies for the National Minimum Wage (NMW) shall be remunerated by their employer, in respect of their work, in any pay reference period, at a rate which is not less than the NMW.
The rate of NMW at which a worker is entitled to be remunerated as respects work, in a pay reference period, is the rate which applies to the worker on the first day of that period.
With regards to your specific situation, there is a lot of information that would be required, which is not appropriate in an open forum discussion, in order to provide specific advice on your status; and therefore which pay reference period is correct to you. For instance, Section 34 of the National Minimum Wage Act 1998 may be applicable, but without a complete understanding of the full arrangements in place, HMRC would not be in a position to comment.
If you require further assistance, please consider seeking independent advice, such as, by contacting the
Advisory, Conciliation and Arbitration Service (ACAS), or an independent legal advisor.
Thank you.