Neighbour just cut down hedge where blackbirds nest

hello petros30;    sorry to hear the established hedge on your neighbours property was cut down and can imagine the disappointment of seeing its disappearance but the removal/trimming/cutting back is permitted outside of nesting season which would be between October and end of February.    The only thing I can suggest is that on your side you grow shrubs like pyracantha or replace hedging with yew (taxus) or buxus which once established will be provide suitable nesting areas for blackbirds, robins, wrens, etc,     It is only illegal to remove active nests within the breeding season months (March to end September)  as it this would contravene the Wildlife & Countryside Act 1981 and be against the law.   Most people like your neighbour leave heavy pruning or removal until October - end February to keep within the law.       Hopefully, you can get some fast growing or established shrubs on your side of the boundary and try replicate what your neighbour took away; sadly, it might take a couple of years or more of growth before it is suitable for birds to nest in.    Regarding artificial methods,  I would stick to natural planting and maybe add some bird nesting boxes and also open fronted nest boxes at lower level to attract ground nesting birds like robins and wrens;     just ensure they are not easily accessible (if placed on a fence line) by any predators such as cats.     Bird boxes for tit birds should be placed higher, more than two metres off the ground facing north/east direction.