That is a bit extreme, but 99% of fungus do no harm, they just look a bit 'off'.
Hard to get rid of too, as anything you might use would also kill off the Sempervivums.

I think you should just scoop them off for the time being. They are feeding on some old wood or debris beneath the bed. You could remove the plants and investigate and if you are really fed up with the look then remove the plants, clear the soil to about six inches and place a sheet of plastic and puncture it and then replace with new soil. I do add that this practice is a bit extreme.

wow! that is amazing, but as said they are probably not doing any harm, but do not eat them. Remove the toadstools and put them in the council green-waste bin if you have one. They will produce spores [seed like structures] if left.

There will be something being broken down that was growing in the soil. Natures tidy-uppers and with all the rain they will be happy.

Thank you for you inputs.
I think I may scrape that area as suggested and replace with some fresh soil and see what happens as don't want it to spread too far, it's more unsightly between times when they die off !