Thanks for that, Odders, very useful to know where it has got to. I'm looking at mine every day, secateurs at the ready.
Just a thought - have you had very heavy rain, interspersed with bright sun? Just look on the backs of the leaves & make sure you have a faint white halo of mould round the damaged bits. It's just possible you have physical damage to the leaves, not blight. (If you're not sure I'd get in & chop it, better to be safe!)
Windy.