I mainly punt in London and the fact is if you do a post code search on AW the majority of profiles that turn up will be zero FB, the phone number has long gone if it was ever there in the first place and the last time anyone logged in was probably some time ago.
The vast majority of these ads are PG scams and the person(s) behind them probably have many more, there just fishing expeditions. Another way to make a genuine ad stand out is by adding amateur pics regularly, fully clothed is fine and a date reference would help, that day's newspaper something like that. But as far as I'm concerned nothing beats cross checkable FB and if I see one of my AW Gurus has left positive FB well that's the gold standard of approval.
I'm sorry but but the odds are so stacked against a zero FB being genuine it's just not worth the risk.