What to Wear
The decision on whether to change out of the wedding dress is totally personal. Nowadays, many brides decide to stay in their dresses, but there is no hard and fast rule.
The bride's leaving (or 'going away') outfit is usually some thing new and quite smart - many brides see it as a chance to invest in a memorable outfit that can also be worn on honeymoon.
If the bride stays in her dress, she will often wear a shrug or cover up; some choose to slightly change their look by taking down their hair or slipping on flat shoes.
The groom may wish to change out of morning dress into a suit, or just stay as he is. If he is wearing a rented suit, he should arrange for someone to collect it from him the following day or return it himself.
If the bride and groom are going straight to the airport, then obviously they will need to change. Any going away outfits should be at the reception in advance and a suitable changing area allocated.
See The Best Man: After the Day