Re: The "funds from Europe to Britain" are important only for a few people -
Farmers often do not look after the countryside, mainly keeping it as lacking in wildlife as they possibly can - close grazed fields or huge monocuture fields are not that great for wildlife,
Some farmers do helpful stuff like leave trees & hedgerows, limit spraying, leave wildlife areas at the edge of fields etc, but too many just want to "maximise" ever square metre of land use to detriment of wildlife.
Gardens can be quite good for wildlife so could be that building houses would increase overall wildlife per hectare ... not that I recommend that, letting any "failing" farmland post brexit rewild would be a better option than houses for willife.