I know of a 2 month old Clementine and her parents are far from posh (in fact, the opposite).
I totally agree with Rufus and Wilfred - I know at least 5 of each under 18 months. Other names which are already nearly up there and I would class as already trendy are Felix, Arthur, Jenson, Albert (all Bertie names), Zane, Dexter, Arlo, Rafferty, Jude, Reuben and Elijah.
Girls are Clementine, Mabel, Edie (the new Evie?), Iris, Ivy, Delilah, Elodie and already 'trendy' but will continue to rise.. Esme, Florence, Martha, Darcey, Tabitha, Matilda, Skye.