As part of the mortgage charter, lenders have committed to ensuring that your credit file WON'T be negatively affected in any way if you opt for one of the measures outlined above.
The practicalities of exactly how this'll work vary by lender, but in general:
The fact you're repaying less each month WILL show on your credit file...
...But there'll be no marker or information added to your file that suggests you're receiving mortgage support (or even an explanation as to why you're paying less than before).
So, while other lenders will potentially be able to see that you're paying less in mortgage repayments than previous months, they won't necessarily know the reasons why.
Where you do accept mortgage charter support, your lender should clearly explain the impact that particular measure will have on your credit file, if any. If you're unsure or confused about it, do reach out to your lender first to get more information on what it could mean for you.