Hi Asif,
When first signs of blight appear on tomatoes it’s usually already too late to do anything. With yours it’s definitely reached the fruit, which means it’s not worth picking the green ones. Because even if they don’t look it, they are infected, too and will get brown spots sooner or later. Sorry!
Next year try blight-tolerant varieties such as Primabella, Primavera and Resi. They are the first results from a project of the University of Göttingen in Germany. Seeds are available through https://culinaris-saatgut.de/en/shop/ They ship to England and you can pay via paypal. See my photo attached: It shows Primabella in comparison to Rotkäppchen, a determined variety usually grown in pots. I didn’t have time to do any pruning on Primabella and when I planted them they almost died due to sunburn. They only just started cropping but are enormously vigorous as you can see. I’ll definitely have some more next year.
As a general rule it can be said that the bigger the fruit on the tomato the higher the risk of blight infection. That is also the reason why varieties such as the tiny Golden Currant and Rote Murmel (we call them wild tomatoes in German) stay healthy when grown outdoors. The genetic tolerance of blight seems to be linked to fruit size.