Right, I'm definately not going to wear a suit, or a kilt. So it's sort of a toss up between :-
Black 'jeans style' trousers (not denim) with a smart, probably white shirt, a waistcoat of similar colour to Ibby's dress and a tie of some sort (not sure on colour)
or
Same trousers and shirt a above witha pale linen jacket and a tie to match Ibby's dress.
Ibby's dress is
http://www.karenmillen.com/fcp/produ...od903000052444