Sorry have just edited my post.
So how to work it out.
Use freebmd and do a marriage search for a particular year and quarter in a specific registration district from the drop down box.
Once you have the results, copy and paste them into excel or other spread sheet.
Then do a sort by page number.
Freebmd returns the replies alphabetically by surname.
Once they are in numerical order go down the list carefully. You can (temporarily) overlook the numbers where there are unceratin character marks or ones in italics which are out of the page range sequence. I sometims do this, look for the oddballs, work out what they should be by having nother look at the imnage and then send corrections to freebmd.
There should be 4 names per page number.
The sequence started in 1837 was by church alphabetically so for example you would have All Saints, then Holy Trinity and then Saints by name so Andrew before Matthew and John. etc
However over the years the order has changed as parishes have got bigger and more churches established.
back to the numbers, you are looking for a break in the numbers, the first and then subsequent parish always start with an odd number.
If you can establish which church is the first in the sequence look down the numbers again - an example 337, 338, 339, 341 and note the breaks. In the example the church should change at 341.
It doesn't work where there are 2 or 4 entries on page 338, the next parish will start 339, not 341
You can work out where these ones are as the list of numbers may be obviously too long.
What may be vital is having access online to the parish registers either at ancestry or findmypast as you can use them to work out which entries belong to which church.
