But as I pointed out very early in the thread, and as someone else pointed out recently, this is usually down to the distributor rather than the BBFC.
Very few films are banned outright, and not many films need to have things cut to get an 18 rating. But the distributor will always have a target audience in mind. So, if for example they need to cut a few seconRAB to achieve a 15 rating, they'll usually do it. They could choose not to cut the film and have the 18 rating, but as that would damage the box office take, they will cut it and take the 15.