The comparable data runs from 1997-2018* and basically confirms that while the percentage of people going to services at least once per year has only dropped from 34.6% to 29.5% (or 18.1% to 16% if we just look at weekly/monthly attendance) the percentage of people who say they feel like they're not religious has gone from 41.1%-53.2%.
Which is to say - Only 2-5% less people are going to services, but 12% less feel religious. This matches my feeling that a very large chunk of the drop in religion that's reported isn't actually people abandoning religion, it's people who were never religious in the first place becoming comfortable that they can say so out loud.
This is particularly pronounced in Scotland. "No religion" has gone from 36.3% to 57.4% while service attendance has gone from 41.1% to 27.2%. i.e. 14% less attendance but 21% less religious association.
We're due another census next year, and I'm very curious to see what it finds. The British Social Attitudes finds a massive correlation with age (33% of over 75 year-olds are Anglican, 1% of 18-24 year olds are. Data here), and so I'd expect society to be slowly aging out of mass religious belief.
*Membership is table 2, attendance is table 5. The attendance question was asked differently in 1991, and the membership question wasn't asked between 1991 and 1997. So the first year we can get answers comparable to 2018 in both tables is 1997.
Original post on Dreamwidth - there are comments there.