Hey OP, I'm about to have an NHS crown fitted on an upper molar which was more filling than tooth. Filling broke a few weeks ago.
Avoided root canal, but the NHS crown was £360 (metal) and the private one would be £980. There was an in between option (porcelain?) around the £600 mark which he said wouldn't be as hard-wearing as the other two.
Mine has been more silver filling than tooth for a long time, although weirdly the temporary crown is white while I wait for the actual one to be made. My dentist didn't try to encourage me one way or the other, just said the main difference between the two is the colour. I was super nervous but actually I think it might be better than the massive filling I had long term, and my priority especially on an upper back tooth is longevity and wear, not how it looks.
I think there may be different guidelines for bottom or front teeth as I have a white filling on a lower molar that I'm fairly sure I had on NHS but it was a long time ago.