A huge amount of research has been done (including, of course, the Conker Tree Science project!) to try to investigate how our horse-chestnut trees might be saved from the threat of the leaf-miner.
The leaf-miner won't kill the trees (although some evidence suggests that it may weaken them). However, the trees are also suffering from bleeding canker which can kill the trees. Most horse-chestnuts in Britain are planted, but no one is planting them anymore because the leaf-miner makes them look so ugly. So in a roundabout way, if there is no solution to the leaf-miner (or the bleeding canker) then this could be the end of horse-chestnuts being common trees in parks and towns.
Possible solutions include: