I don't know the numbers for the UK but here [1] are some numbers for Bavaria with worm counts from a lot of monitoring spots starting in the 80s. (sorry, slides are in German)
In the conclusion the author says a connection to the tilling method is likely. (worm numbers in Bavaria actually have increased as more and more farmers have changed away from "full" tilling).
Sorry, I should probably add that the worm number also very heavily depends on the kind of ground you have on your fields. In case that is not apparent from the slides ;-)
In the conclusion the author says a connection to the tilling method is likely. (worm numbers in Bavaria actually have increased as more and more farmers have changed away from "full" tilling).
[1] https://www.lfu.bayern.de/boden/bodendauerbeobachtung/fachta...