I would really class it as the final action before arrest in these cases, and anyone who in my eyes would complete the criteria for a S27 notice will be given their fair share of opportunities to leave voluntarily before issuing a S27.
Our supervisors will actively encourage us to dish out S27's at the first signs of trouble, the theory is that those causing trouble will only get worse as the night goes on.
I am quite happy to issue them when people come to notice during our op marble (night time economy policing), even more so when people fail the attitude test. There was one incident when a woman had been jumping on a sofa in the bar, she hit a speaker and damaged it. When approached by the management she refused to give her details saying that it was easily fixable and that she would do it. They did not want that being 11pm and semi dark so they took her outside to us, we explained that it was in her best interest to exchange details but she still refused, she did however say she would give her details if we dealt with it officially. As a result we had to issue a community resolution to her which was a massive pain in the rear and as a little present she got a S27 for her troubles, she was on a hen night and was not impressed, told her she should have listened and taken our original advice.