In reply to Timmd:
Hello Timmd
Might be worth looking at the Biodiversity Action Reporting System website. I be surprised if there is good data to be certain where/how the BAP actions have been undertaken, or if so, have been the determining factor in species increase/decrease. So many other things in play since the UKBAP first written, not least ever changing agri-environmental schemes and governments.
That said, species are more easily measured, and otter have been going great guns so might be worth having a look at. To inform your view, it is also perhaps worth reading the RSPB State of Nature report, if you haven't already.