Are you planning on a spiritual/religious ceremony? Or just registry office? Or something humanist?
The only downside to an autumn (prettier word) wedding would be the unpredictable weather. It'd be beautiful to have an outdoor ceremony but hardly practical in the event of a storm, or gale force winds.
However, an indoor location can be decorated in those lovely reds, oranges, russets etc which are more appropriate to the season (not to mention more stunning) than the pastel shades which tend to be favoured in the spring, summer and winter.
Congratulations
