One last suggestion – join your local gardening club or society…Never mind the camaraderie, the social events, the plant sales and, if you are a little bit competitive, the shows; your fellow members (most of whom will live near to you) will happily tell you if a) they grow Box and b) if they do, whether or not Blight has struck.
In fact, and this applies particularly if you are already a member, why not obtain a large scale local Ordnance Survey map and mark on it (those little peelable sticky dots are ideal) where Box is growing (green) and where Blight has struck (red). Members can be encouraged to ask their neighbours and other locals the same question. And a short letter in the local newspaper can request yet more data. With very little effort and expense, you’ll quickly build up an accurate and extremely useful picture of Box Blight in your area.
Forewarned is forearmed – and you may discover your locality is Box Blight free!