wow! thats a shocker. I had an observation once and only after was told she was an optom. but said that she wanted to make sure i was recommending the products.
I dont use the slit lamp often, it is not possible always due to time constraints and of course not always absolutely necessary.
i suspect if you had recommended all their products they would have let it go!
If they have a problem with your routine test then their optom should discuss with you so you can explain your decisions or tests. just a cancellation based on one observation is ridiculous procedure. But not surprising to be honest from Boots. Nothing seems to be too ridiculous these days with them.