Nobody can say how likely you are to get an offer, and everyone who is saying you probably will is being deliberately misleading. It depends how popular the course is, and what the general policy is. Although some courses advertise certain requirements this doesn't say anything about the quality of the applicants - many people will apply with better grades. For example, York used to ask for ABB for Economics, but if you weren't predicted higher you were very unlikely to get an offer. Edinburgh doesn't like anything less than a B.
So no, there's no such thing as "many universities will give offers to applicants who are predicted just one grade lower than your target grades". If anything, it's the opposite.