The etiquette was simple,you went where the photographer told you to go.The important thing about large groups was getting the balance right.Having said that there was an order to it with the close senior members seated near their relative.
The bridesmaids are traditionally family & friends of the bride & the one seated next to her I would say is a sister or cousin,the others being spread out to give balance.Married couples would be together & if one was seated in front one would expect to see their partner behind.The best man would be in the vicinity of the groom but could be any of the 3 young men behind him.After that it was down to how many were there from each side,these would be spread out across the photo.
I would expect the second row to roughly equal between his & hers.
The cost would be down to what they did afterwards,wedding receptions were rare.They don't look particularly grand so sherry for the ladies & beer for the men I dare say.
As for a date I would suggest 1903-8.
Edit:Had a closeup look & I think I can tweak it up a bit to 1906.
I notice the older woman sitting next to the man with the Newgate frill has taken off her left hand glove to display her wedding ring,a common practice for married women.
The man on the left looks like the father of the groom with his dog so one might assume this is in his garden.
The question for me though is how did SuBo get in there?
jim