I knew a lovely Jago at college. One of the poshest people I've ever met, but in a lovely not at all wankerish, very charming and kind and considerate way Any mum would have been delighted if their daughter had brought him home!
Having said that, not sure it is a posh name as such (unlike Tarquin say which is one of those posh people only names) so don't think you need to worry about inverted snobbery or sounding too posh etc.
I like it, and is on my list for DC2 if a boy.