"The fact is that Britain's society has changed due to an incredible number of forces at work, and to see that as decline is silly, considering how much better off I am personally than my grandparents and certainly the generations before."
To use a measure of material wealth as the yardstick of how "better off" a society is, is itself a sign of how you are worse off than previous generations.
"If 66% of people do not believe in a deity, surely as long as both they and the minority are free to live by their beliefs there is no cause for alarm."
If 66% of people do not believe in a deity, then they are not free, and before long they will be using force to enslave those who do believe as well.
What metric am I supposed to use instead of the fact that most people are no longer living hand-to-mouth, Tantumergo?
"If 66% of people do not believe in a deity, then they are not free, and before long they will be using force to enslave those who do believe as well."
No one is being coerced by the state to follow a religion or not, and no adult is required to tolerate anyone trying to coerce ver: I consider this a more accurate approximation to being 'free' than whatever concept you might have. I fail to see why non-believers would use coercion.
Perhaps you are referring to the concept of being spiritually enslaved. This is a logical contradiction (read: absurdity) if you don't have religious beliefs.