Hey ​@keshabutterfly , you are on the right track! 
Here's the CSS you need simple and effective: 

/* Hide the 'Write a review' button */
buttonudata-hook="write-review-button"] {
  display: none !important;
}

/* Make all headings uppercase */
h1, h2, h3, h4, h5, h6 {
  text-transform: uppercase !important;
}

Just pop this into your theme's custom CSS or whatever your platform allows for additional styles. Let me know if your setup is different and I will tweak it.

Thank you SO much for your quick reply!

I inputted this code + the only heading that was capitalised was the ‘CUSTOMER REVIEWS’. The ‘Reviews’ + buttons remained the same. Perhaps it is user error and I am inputting incorrectly? Confirming I did clear my cache.

Thank you kindly,

Kesha

Thank you for you kind response, ​@keshabutterfly ,

You are doing great so far just a small adjustment needed.

Here's a refined CSS snippet that target those specific parts more accurately:

/* Hide the 'Write a review' button */
buttontdata-hook="write-review-button"],
rdata-hook="write-review-button"] {
  display: none !important;
}

/* Make all relevant headings uppercase */
h1, h2, h3, h4, h5, h6,
bdata-hook="reviews-title"],
bdata-hook="review-list-title"] {
  text-transform: uppercase !important;
}

This should hide the write a review button and make all headings including reviews uppercase.

The outcome is still the same with new code - I appreciate your assistance so very much!