Actually I wonder if it isn't just someone having a laugh at someone elses expense.
First the title of the ad Blonde with big tits - 21 (durham ) Most, not all, but most women I have ever been with, professionally or personally never refer to their breasts as Tits
Second the "are you looking to party with a hot blond" ok so lots of women will talk this way, but imagine for a moment someone trying to get some revenge, say an old boyfriend or girlfriend saying this. It fits as well
Third the spelling on the next sentence is awful, almost like someone who was drunk when they typed it, and the hours of 8 - 3 ok that is doable but it also when a lot of people have settled in for the evening and if you were trying to piss someone off by having their phone ring at weird hours this would work as well.
I just see this as a possible "funny" ad rather than a serious offer of service