The postgraduate loan is repayable at a lower income threshold, but at 6% of the excess, vs 9% for the undergraduate loan. So if you are over the repayment threshold for your Plan 2 loan, you will pay 15% above £25 725.
From the gov.uk website:
If you have a Postgraduate Loan and a Plan 1 or Plan 2 loan
You pay back 6% of your income over the Postgraduate Loan threshold (£404 a week or £1,750 a month). In addition, you’ll pay back 9% of your income over the Plan 1 or Plan 2 threshold.
Example
You have a Postgraduate Loan and a Plan 2 loan.
Your annual income is £28,800 and you are paid a regular monthly wage. This means that each month your income is £2,400 (£28,800 divided by 12). This is over the Postgraduate Loan monthly threshold of £1,750 and the Plan 2 threshold of £2,143.
Your income is £650 over the Postgraduate Loan threshold (£2,400 minus £1,750) and £257 over the Plan 2 threshold (£2,400 minus £2,143).
You will pay back £39 (6% of £650) to your Postgraduate Loan and £23 (9% of £257) to your Plan 2 loan. So your total monthly repayment will be £62.
This bit is interesting, however:
If you have 2 or more jobs
If you’re employed, your repayments will be taken out of your salary. The repayments will be from the jobs where you earn over the minimum amount, not your combined income.