LCWRA NHS dental costs help

Hello, I am currently on LCWRA and have been for over a year and I know that it entitles you to free dental care on the NHS for most things. I'm just a little confused. I go to a dentist that accepts NHS and private patients but I have shown them my exemption form. I recently got two white fillings done of which they cost £150 each which was what I was told that I had to pay the private price as they were white. My housemate who is also on LCWRA who has the exact same dentist as me and also got fillings recently and told me that the dentist told him that because he gets free dental treatment on the NHS he would only have to pay the excess charge for the white filling which would be around £50-70, however he opted for the silver filling anyways. I'm just a bit confused, have I been overcharged for my fillings? Should I have only had to pay the excess for the white filling? I feel incredibly stressed now as it was a lot of money.

I was also told that I needed to book a cleaning with them that cost £65. I thought cleanings weren't covered on the NHS and so I paid it. But apparently they are? If so why was I made to pay the private price? I'm just really confused about how this all works