The Parks Trust has reported that Ash Dieback disease Chalara (Hymenoscyphus fraxineus) has reached the Milton Keynes area. You can read their press release here.
Mike LeRoy has provided the following additional information –
The most reliable national source of information about Chalara is from the Forestry Commission website.
A look at their map of occurrence of Chalara shows that over half the 10km squares in England have occurrences of Chalara and its arrival in north Bucks and MK is relatively late, not least because the first national report in 2012 was from horticultural saplings elsewhere in Buckinghamshire. Advice for gardeners about Chalara is given on the Royal Horticultural Society website.