The disease seems to have emerged from a fungus that was previously a harmless saprophyte.
There is a cheap copper solution that can be applied (said to be £1 per acre) which could possibly kill the fungus.
This should be tried, but it would possibly need to be applied year after year - which would need a lot of work. I'm all in favour of creating work, but the employers might moan, unless it were under the Green Wage Subsidy. Also there's the matter of toxicity. So copper might be restricted to a niche, like arboreta.
I remain convinced that we should be calling for felling of infected trees, and santiary felling of healthy contiguous trees. This and other measure would slow the (inevitable) spread of the disease, making it less traumatic. Felling healthy trees means that the wood can be used, which is good (wood is a carbon store). In the clearings left by the fellings, ash seedlings will spring up, and 2-3% of these will be immune. These should be protected and nurtured, so that in 50 years (no time at all in foresters' time) our ash populations will be restored.