I call her Matilda, I never shorten it to anything but there are a fair few people on both sides of the family that call her Tilda, actually this is the only thing that people have ever shortened it to and I really do not like it but oh well.

Mind you I do not mind if her grandparents use it so much but it seems everyone does!
Our Matilda is Tilda to everyone too - we never intended for her name to be shortened to that, but when she was born her older brother and sister had trouble with saying Matilda, they always said Tilda. So Tilda it was, pretty much from the day she was born. I don't mind it so much. She also gets Til, Tild, Matilda-bot (from DH), Tildie, and Mopsy (from her grandparents, because she had a 'mop' of hair when she was little).