Morning Robert
Welcome to the Forum
😂😂 I do hope that whoever told you that has a twisted sense of Humour
If your windscreen is in good condition (ie. No cracks, deep scratches, scores and chips that obscure the drivers vision = MOT Fail) So assuming your screen is OK read this Jenksy who has a 6 series has just posted on the fix for the same problem.
""Hi all, I got the adhesive that was recommended in a you tube video with instructions, it was from Permatex. I had to ensure I removed the old adhesive from the silver disk first which took some doing but needed a sharp knife and a razor blade to lift it all. There was no adhesive debris on the wind screen.
To fix I then used a wipe supplied in the kit and used a small amount of the adhesive also supplied. The bond took less than a minute. You do need to be sure of the location as the bond is very quick so ensure you can locate the mirror accurately otherwise it is going to get messy.
N.B. I had to remove the two connectors to ensure the mirror could be located properly. It was a little fiddly getting them out but went back once mirror was fixed to the windscreen. A good experience though for me and mirror is back on with the accompanying casing parts also."
Hope this helps