When you are signed in to 'Manage my Mortgage', you will be able to see 'your monthly payment'.
This amount is the minimum you are contractually obliged to pay each month, but it doesn't include any regular monthly overpayments you may have set up.
The minimum monthly payment is also broken down for you under 'The detail' section, where you can see any sub-accounts you may have and how much they represent of your monthly payment.