Look at online lists of current popular names (make sure they are British, not American , unless you’re American), and then you can see what is top of the list and maybe avoid those because there will be too many of them.
I like unusual, but I think it’s always best to use a full name and not an abbreviation. They can use the abbreviation in everyday life if they like, as many people do.
I gave each of my sons one fairly unusual (but traditional) name and one more ordinary one as a middle name, in case they preferred to use the ordinary one when they grew older. Neither chose to do that, though. The middle names were James and Philip, but I’m not telling you their first names!