Cornish hedges - which look like dry stone walls to others - are undoubtedly a good habitat for lots of creatures, and probably important to use the local stone if you want to encourage the local flora - concrete is not the local stone.
I don't think it is necessary to convert pasture land to piles of concrete rubble land though - when there are hedges and small corners of most farms doing this work already. On my own mini patch I have an area where I stack up useful rocks and bricks for future use, and I have grass snakes and slow worms making good use of it, but it isn't where food or grazing could be grown.
Cornish hedges very similar to Pembrokeshire hedges,with the earth infill and the outside stone sloping inwards.
Seems the Welsh Labour Government has its sights on wilding Wales with its plans for reduction in livestock and tree planting,they cannot manage properly the tree`s they have now.
I always avoid the 'free tree' and 'free wildflower' seed offers. They are usually the wrong species put in the wrong place. We also try to stop people planting things in our wood as the result could be catastrophic. I have removed hyacinths, but left the mini daffodils. The hyacinths would have crossed with the native bluebells, but the daffodils won't do too much harm. As for well intentioned people planting trees; waving them around in the air or laying them on the ground before putting them into a nice big hole, they are just wasting effort and tree seedlings.
Personally, I have found the Forestry Commission very supportive. We have semi natural ancient woodland, and they may suggest ways we should change our management slightly, but have never told us it was wrong or we had to do something else. I suspect your conifer plantation would now be in line with policy; remove conifers and plant mixed native species. There is now a backlash from the foresters who grew up in the plantation age saying where is our timber for building going to come from (it will have to be imported). Probably a mix is the best policy.