I don't think Harry and Florence are together because firstly no one I know has heard of something substantial happening between them. Also there are several evidences to prove the same :
1)Daily Mail article
http://www.dailymail.co.uk/tvshowbiz/article-2075645/Is-Prince-Harry-lingerie-model-Florence-Brudenell-Bruce.html" She explained that she found the public attention quite 'full on' and that had dies down since they stopped seeing each other.
In her first interview since the split Florence, who grew up in Fulham, south-west London, revealed that she is keen to pursue a different career as 'one day everything will drop and I won’t be able to earn my living in a bikini. "
Florence's quote sends out a clear message. If she and Harry were romantically involved earlier, its over now.
2)
http://wasaphollywood.com/wp-content/uploads/2012/01/bb64_florence-brudenell-bruce-tatler-january-2012.jpgNotice she was on Tatler's January cover, IMO no royal girlfriend would go about going interviews about the "relationship" even before the relationship was officially confirmed or they were seen together. Harry, being the private person that he is, wouldn't go for a girl who would snatch up a Tatler cover using his reputation to take her career forward.
3)The Tatler Cover photo
http://wasaphollywood.com/wp-content/uploads/2012/01/8e48_florence-bruce-tatler-0112-7.jpgThe tag-line says "The One That GOT AWAY", again it implies that whatever was between them (if there was something in the first place) was over.
4) Yes, Harry's had a "wild-child" image forever BUT that's his private life when he's out clubbing etc with his mates. In his royal duties, Harry's record is clean. He is sincere towards his duties as a royal and has never compromised on it.He understands he has a certain level of responsibility when he chooses his life partner. So I don't think a lingerie model (though she is also very much involved in art) is the one. Even his last girlfriend Chelsy, inspite of the haters, she could be a potential royal, I just don't see the Queen or even Prince Charles for that matter, in the same picture as Florence.
5) No picture of Harry and Florence!
The whole FWB option seems likely though.