18th Birthday

Its my 18th birthday in 4 months, all my friends will still be 17 so it really limits what i can do for it, i don`t want to do anything childish or have a house party and im starting to save £10 a week until the day not a lot but its something, my friends have suggested an ann summers party but i still feel too young to do stuff like that even though i must admit it would be a laugh, help!