wa 3alaikom assalaam
How come you only come in here to advertise?
Not all of us are in london and so how would we verify that the people you are advertising for are 100% ok.
When it comes to matters of Religion, that is how sure you must be.
Like when you need a doctor, you need to find a trustworthy one who is truly committed to their job and studies their work and wants to help people - so that any diagnosis they give to a person can be trusted.